Having sex

I literally am horney all the time now that I'm pregnant but every time we have sex we get like 30mins into it and I'm so tired I just want to be like nevermind I changed my mind...😭 I love sex with my husband and I want to have sex but I feel so worthless because now that I'm getting a belly for the baby we can only do a couple of positions and I feel like our sex it's that good to my husband anymore because of that and cause I get so dang tired??? Is this just me or is other couples having theses problems????