Jelaousy

So, I have a problem. I have a boyfriend for year and a half. He told me he does not watch porn. I said okay, but one day found on his laptop '18 year old wet ****' .. I felt awful. Because, I'm 18 years old like.. you have that from me why do you need to look elsewhere. But I tried to be reasonable, I know he has to get off sometimes, and I said i will send him my photos, videos, anything he needs! He said he wouldn't watch it again. Later on I found that he looked his exes profile on facebok, and I was like whhhhhy dude can you stop hahah like the girl was sending him messages all the time back when we just started dating and I dont feel comfortable if he checks up what's hapening with her life. He promised he wont look at other girls that he had something with. I said okay. It was rough. I cried and cried and felt like i am not giving him what he needs. 3 months passed since that. And. Ah. he opened history to delete it cause internet was slow, and I saw he was checking facebook of a girl he had sex with before.. I really dont get it. Why do you need to look at them. I see him every day. I dress up for him, make his fantasies come true, i have a ton of lingerie, i can be dom i can be sub, i am very open to new things. I have sex with him 5 times a week, send him nudes, everything...
I started crying and he said that he just forgot that he looked at that and he wont ever do it again
what do you think should i believe him? that he wont do such a thing to hurt me and make me dissapointed again?