Sex life help 😣😣

My husband and I literally have sex maybe once or twice a week. Sometimes not at all. He likes when I ride. I used to love to do that but now I just feel fat and like I'm hurting him. Lately he has been asking me to get him off and I try I just get tired or start hurting. I'm 4 months pregnant with our 3rd child. We had sex like 2 nights ago and he got to hot and asked me to ride him I did for 15 mins then started to hurt because of the way I was doing it n asked to switch for a few and he pushed me off got up said I turned him off n got dressed. Pretty sure he did it himself later which I don't mind but I do because that's supposed to be my job.. I guess what I'm looking for is ways to try and please him better without feeling the way I do. Ways to ride with getting cramps or hurting. I love my husband with all my heart I do I want to be the girl I used to be and get him off and not feel like I do. Any suggestions??