i need help

So i’ve been in very toxic relationships in the past.. i’ve been cheated on in 2 out of three relationships. I was about ready to give up then my boyfriend now came into my life. We went to high school together but i’m a year older than him. Im still very scared of getting my heart broken again. When he is with me his phone lights up all day and he never checks it but when he does he turns away from me which i don’t mind. Then he hangs out with his friends and he doesn’t text me or anything the whole time but his snapchat scores goes up. should i be worried he is cheating on me or what’s going on when i talk to him about it he just tells me “ i’m sorry i’ll fix it but he isn’t trying....” i’m just hurt and need advice.