what should I do?

I have been with this guy for over a year now. Our relationship has been on and off and we are very complicated. I am so in love with him and he knows it. He says he loves me but sometimes I feel as if he doesn’t cherish me, he doesn’t care, and I wonder, would he be heartbroken if he lost me? I had my friend text him one night to see if he would reply to her because we had gotten into a fight and he hadn’t been texting me back. He replied to her while I was still on delivered. She asked what he was doing and he told her, eventually he responded to me and when I asked what he was doing he straight up lied. I don’t believe he would cheat on me because he’s been cheated on. He knows the feeling. I feel like our relationship is too strong to be killed with cheating. But there’s always the feeling that he is cheating, and now that i’ve caught him in a lie? I just don’t know what to do. I cant see my life without him, and imagining it hurts. I ask my friends what to do and they say to leave him. But I cant, that’s why i came here to state my situation. Hopefully someone can help me out.