Why is my husband watching porn now?

Me and my husband have been friends for 10 years. We started dating when i was 20 and he was 22. We got married when i was 23 and he was 25. I am 24 now and pregnant and he is 26. So basically we have been together for 4 years now. And yes he is faithful to the fullest and sweet and thoughtful. He has always been like this since i knew him and very honesty. My mom loves him my whole family loves him. He did not watch porn while we where dating. And then after marriage he has watched it 3 times for just 1 minute. I found out because he had it in his history of his ps3. And the first tim i confronted him he said he did and apologized and said he would not do it and then 3 months later he did it again. And i found out. And he said he did and said he swears he will never do it again. And he has never hid anything from me or even lied to me about something as small as that. I thought he never watched porn while we where dating and i believe he did not because like i said i know my husband. And if you know him and grew up with him you would know he is very honest and alot of people love him. We have been married for 7 months now and we had those newlywed arguing in the beginning but now it has gotten better where we communicate about what is the problem. And another thing i am 26 weeks pregnant and don't want sex period i don't want it at all since i gotten pregnant. And when we where girlfriend and boyfriend we only had sex 1 time a week and he did not look at porn. So i don't basically trust him anymore i have always trusted his word when he said he would not do it again. He says he is not attracted to them at all and does not want to have sex with them. He only looked for 1 minute or 2. I have watched porn while we where dating about 4 times and it does nothing for me and i don't want those people.Can someone give me some advice. I will probably never trust him again and i looked him i the eye and told him this. He is in love with me i know this and everyone knows this and i am in love with him. And it shows from both of us. Give me some advice please. And don't tell me to join in or get over it. That is not gonna happen. I just want to know why now. I asked him why and he said he does not know why.