Ni Hao
I am very sorry to hear your situation, but you need to make plans. You entered on May 21 which means your time will expire on August 21. If you want to ever want to legally come back again to the USA you need to not have an overstay on your record. I would shop now for the cheapest flights back to China and just go.
Your fiancée is a bad person. He is an immature boy to have strung you along this long if he did not know he wanted to marry you. Drop him like a hot rock. Very sorry to hear your story, but there are many fish in the sea. Next time I hope you find a prince and not a selfish pig.