Starting to feel bad :/ 31 weeks

I’ve turned 31 weeks and my sex drive us just not there... I love my partner so much and I can see he wants it and like I still find him so attractive but I just can’t get in the mood! It’s more effort and awkwardness then pleasure but then I feel bad I’m not satisfying him. It’s just when we do it I loose my breathe and find it hard to breathe and whatever the position I feel pressure and also I don’t want him to see me naked with stretchmark ect :/ help