Nausea during/after sex? Please help!

I feel like my whole pregnancy I haven’t been able to have sex with my husband because I get so nauseated during it and then if I last the whole time, after we get done I feel like I’m gonna puke and sometimes I even start gagging. It’s gotten worse since I’ve hit my 3rd trimester. I feel so bad for my husband cause every time we try now I have to make him stop because I just feel so sick and it ruins the mood for me. Anyone know of anything I can do to prevent the nausea during/after? Is this even normal?