I have an older lover and I need advice

I’m 16 and my bf is 19 and my mother does not like us being together at all because of the age difference but we love each other or so we say, my mom keeps on putting thoughts into my head that he’s cheating on me and that he doesn’t really love me he just want to put me through hell even tho I think he’s a nice guy because when we first started dating we met in the same state and later on I learned that he lived in another state an needed to go back but ever since he’s been back we’ve had an on and off relationship and have broken up 4 times and sometimes it’s because he thinks I don’t love him and so 2 days ago we broke up again but we blocked each other and we only did that because I started to lose some of my friends because of our relationship and he didn’t want me to lose them, over all he’s really sweet caring and funny....but one of my friends went on his account the other day on insta and he posted something about him saying he’s on the phone with bae and then that one loud friend says which one....so I don’t know if he was faithful while he was in another state. What should I do?