how do you know if your boyfriend is cheating😔

we've been dating for 15 months and I took his virginity. When we first started dating and what not he would want to have sex all the time and could never keep his hands off me. But as time goes on he's more and more distant and never wants sex. I found porn on his phone once and bawled my eyes out and asked why he did it and he said it was because I wasn't good enough or hot enough and that we didn't have sex the past day and he needed. I tried breaking up with him and he begged for me back and had porn blocked on his phone. But now it's honestly like he can go weeks without sex. I tried to touch him but he pushes my hand off or says he doesn't want too. How is it that he couldn't go one day before but now he can go weeks? I also don't think I'm that un attractive either. Maybe I don't have the best body but he used to love it.Â