Am I wrong...?

So I'm 30 weeks pregnant and the last couple times me and my boyfriend had sex he hasn't finished. He always has an excuse like he's tired or he has to pee or something like that. I've been feeling really insecure and I feel like he can finish because of me. I've told him that and he says it's not that. One thing he always wants me to do is ride him and I do but I don't really know how to like bounce up and down. I can tell he's disappointed. He was off work today so I wanted to surprise him with learning how to do it. I Google tips and watched a video on pornhub. We both don't like it when the other watches porn. He dosent and I dont. But he walked in when I was watching the video and we got in a fight. He was mad and yelled at me. He's forwarded a video on Facebook of tits before and in the past has watched porn and I dident even get that upset with him. Am I wrong for this ? I was trying to do something he would like.... he made me feel shitty and ashamed. Idk what to do.