Missy Crissy

The fact that he did it behind your back, you already know the answer.
My fiance and I are very open about women he still talks to and he knows that I still go to the dating site where we met. But my profile said I'm engage and only looking for friends. My fiance was the one who suggested not to close my door to opposite sex just because I'm getting married, or married in the future. He wants me to socialize still and the last thing he wants to do is cage me. I admire him for saying those things to me and giving me the freedom to spread my wings and I give the same in return. He still communicates with other women, he meet women for me as well. He wanted me to have friends when I arrive in the U.S since I don't have any family or friends there.
If only your fiance told you what he's going through, it would have been different. That means he trust you that you'll trust him. Trust is important. Once it's lost, you'll always have doubts if he's telling the truth or not. Without trust, why stay in the relationship? Don't worry that you don't have anything when you go back to your home country. I'm sure you'll get back on your feet in no time. Women are survivor and fighters. You'll be fine.
Worry about the long effect if you continue with the marriage. You're lucky to find out now, than find out later. Take that as a sign of not getting stuck in a situation that you couldn't get out.

Yup. You have to cancel the first appointment the you can re-schedule. You are only allowed to do this twice, after that you would have to pay another visa fee.