I don’t know what to do...

So my boyfriend is in training for the army and graduates in little over a month. We’ve been dating for a month now. Well I should be honest, I met him right before he left to finish his training after Christmas break. He didn’t ask me to be his girlfriend until the weekend after. He didn’t really ask me though. He just kind of told me that he felt that he claimed me after we spent two whole days together (which were the best conversations of my life). I send him letters and we are getting to know each other. I started catching feelings for him hard. It was the best thing I’ve felt. Then as time went on... we started to talk less. The letters take forever in the mail so I started hanging out with our friends again. Then two of them told me something he hasn’t yet....

He had a fiancé before me and tried to cheat on her more than once with someone who was close to me. Then his best friend told me to not trust my own boyfriend. Apparently she wasn’t the first he has done this to. So I’m currently on a rollercoaster of feelings and don’t know what to do. Lovely time to be cheated on... right?