I really need help! So confused! Please

Autumn
So my boyfriend and I have been fighting a lot lately. 
​We went on a 5 day streak with no fighting and we were happy. 
​Tuesday night I got really emotional due to pms and I got snappy with him. He brought his ex into the argument and compared me to her. Than would talk about it because she's a "sensitive" topic to him. 
​The next day he said that he was second guessing our relationship and I almost lost him.  
​I just don't know what to do or how to feel I'm soo scared 
​Please help. All accept any advice. Please