Pixelx

Back in the day my husband made his first trip to see me. He brought with him no real evidence of anything whatsoever. He was thoroughly grilled by the CBP, he can't remember how long by now, but think something like 20 minutes or so. They threw at him every single question they could think of: and for each question, he remained calm and had an honest answer for. They wanted to know and tested him on everything about me and my family. Looking back I think to myself that without paper evidence and if he had been a lot more nervous or stumbled on some answers when challenged he might not have made it in during this day and age. But of course they liked the fact that he had an answer for everything and he had a return ticket and travel insurance. Since that time he made many trips to visit, and honestly he still never bothered to bring any evidence and was never bothered by an IO ever again either. It didn't matter if he was employed or unemployed or even a student. But I don't think in your case, I would attempt to visit your first time without coming prepared with evidence. Go over any and all questions that could be asked. No one here can tell you how the IO will react, they can only offer their own experiences.
 
Be unflappable, prepared, and always truthful.

I was in a similar situation to you and was able to travel to the U.S. on an ESTA and stay with my boyfriend (now fiancé) for 85 days back in 2015.
 
At the time I was recently unemployed and was living with my parents so I had no ties to my home country. At immigration I told them how the fact that I was now unemployed was giving me the rare opportunity to take a bit of a career break and wanted to take a long break to spend time with my boyfriend with the plan to do a serious job hunting when I returned home. They pulled me aside and 3 different people questioned me for a total of a 45 minutes. They also searched my luggage - I believe they were looking for any evidence that I might plan to work or stay long term while I was in the US.
 
The final officer that spoke to me told me straight out they had good cause for concern and reminded me that I could not spend more time in the U.S. than my home country. I stayed polite and made it clear it was very important to me to abide by the rules. 
 
Yes, it is possible for you to make this trip like me but I'm sorry to say it's not guaranteed, it is at the end of the day at the discretion of the immigration officers. It's so important to stick to the truth! Answer their questions honestly and don't offer up extra information they do not ask for. I wouldn't be too keen on telling them your plans to get engaged - as it has not happened yet it's not important.
 
I know it's hard not to be nervous but once you have nothing to hide and intend to stick by the rules you should have no reason to be worried!!
 
Best of Luck!!!!
 
 

I'm Swedish and my fiancé is American. I visited him multiple times while we were boyfriend-girlfriend, always told the CBP that this was the case, never any issues. The first time I visited him was the first time I had been to the country in a few years, I came alone, and I was on a new ESTA (obviously). So I was "randomly" picked out to have my bag checked and the CPB lady used the opportunity to ask a few more questions. We talked for a little bit, she asked roughly the following:
 
What is the purpose of the trip (vacation)
Are you visiting someone (yes)
Who is it that you're visiting (my boyfriend)
How long have you been seeing each other (nine months)
How did you meet (on an exchange in country X)
How long are you staying (a little over a week)
Where will you be staying (address Y)
What is the address you're staying at (his university)
 
Then she also had some questions about things in my bag (nothing interesting in there though, I promise!). They really don't seem to want to hear long stories, they just want straight, reasonable and truthful answers to their questions. One CBP officer at a later point actually lit up when I told him I was visiting my boyfriend "Ah, so that's why you've visited more frequently lately! Have a really nice stay!" and then he waved me off. 
 
I think bringing evidence of return/ties to home country is a good idea in your case since you're staying for a longer amount of time, but don't sweat it  I think you will be just fine.

I have visited my fiancé in the US twice now (2 and a half months per visit) on ESTA, and didn't have any problems.
 
The first time I was living on my own and had a lease but didn't even think of bringing it with me as proof, I basically just had my tickets with me, to show that I was planning on going back. I flew to Florida and the guy questioning me seemed super nice and casual. He asked the reason for my visit (I think I just said vacation), where I was going to stay (with my boyfriend) and how we met. He also said something like "Oh so that's why you're so nervous!" when I told him I was meeting my boyfriend for the first time, and made a sympathetic face when I told him that we'd be driving for about 7 hours to get where he lives.  Then he told me to have a great trip and let me through.
 
The second time I flew to Atlanta (much closer to where my boyfriend lives, thankfully) and I just had my tickets and boyfriend's tickets (he flew back with me to visit my family) as proof, no lease since I had moved out and lived with my mom at the time to save money. The lady questioning me asked the reason for my visit (to see my boyfriend), when was the last time I visited, how much money I had with me, if I had a job back home (unemployed at the time) and how I was going to live in the US (I said my boyfriend is working and I'm staying with him) and then she let me through.
 
So I was never asked to actually show any proof of ties to my country and they seemed to be fine with the long visits too, I did have about a year and a half between the visits though. Oh and I'm from Finland by the way.  

We were married 6 or 7 years when we visited the US on vacation after flying in from India (I'm a UK citizen, my better half and the munchkins are US citizens). On arriving at Detroit, I was asked 
 
Official: Where did you fly from?
Me: Mumbai, India
Official: How long you planning to stay here for ?
Me: 6 weeks (on ESTA)
Official: Do you have an address?
Me: We own a home in xxxx
Official: Do you have a return flight?
Me: Yes:
Official: Show me?
<>
Official: Enjoy your stay...
 
I wouldn't worry as long as you are straight forward and truthful...