Porn & my dieing relationship

So to give what just happened to me meaning. I'll start at the beginning. My boyfriend and I have been together almost 2 years. In the beginning sex was amazing! I always finished even though it was penetration only which was super rare for me(I was always a touchy and feely gal) well after a year he gained some weight(I like to cook southern meals) while I still love him hips and all. His libido has taken a huge hit. He barely started to touch after awhile. But he was super into porn. I would find it in his phone all the time.( I dont search through his phone sometimes he will ask me to answer it and I'll open it up and it just be there) I told him I felt kinda shitty about it and would prefer him not to watch it but if he wants I can make videos or pictures for him so he can watch something or if it's the fact he is looking at it for inspiration then let me watch too. Now i like porn I dont hateit, I just like it when partners sneak behind each others back to watch it especially when one is feeling unwanted. He has said he just wants to be ripped again and he will feel better and start getting into it again but he has declined all my offers when it comes to making him videos or watching together. It also doesnt help that he watches petite 18yearolds. It really messes up my head and makes me afraid to get old or gain weight to the point where I dont feel like I'm being healthy anymore. I mean he doesnt wanna touch me and we he does it makes me feel like it's just chore and doesnt really try. i havent seen him watch porn since. But his phone went off tonight so I hope to open it and there it is again. Now I'm back in the pit again. I told him and compromised before saying if this keeps happening then I should probably just leave. For my health mainly.i believe in chances but I've wasted so much of my time on people that just used me and I dont know what to do. I've talked to him about it once maybe twice. So I guess wat I'm asking is should I just leave this time? Let him explain himself and give him another chance?

EDIT: I'm not shaming porn I feel like if a SO wants to watch then so be it. But it's when they hide it is when I feel it's bad or when they prefer it over their SO.

EDIT: When I say he has gained weight I mean it like he doesnt have a toned stomach anymore. He has gained about 10-20 pounds. I tell him he is amazing all the time and he will always be my love. I know that sometimes that just isnt enough. Then I also think to myself that why will I love him no matter what meanwhile if i gain weight or get stretch Mark's he will leave me. (He has a specific taste in women and gets grossed out easily)