Sex during pregnancy

My boyfriend and I have been together for 6 years now, come September we are expecting our first baby together. But there has been a huge change in our sex life. This man has wanted sex nearly every day for years. Since I've been pregnant I haven't had much sex drive, but I by no means let him be neglected. But now I'm in my third trimester and he just doesn't try. I don't know if it's my belly, I also have stretch marks on my sides and thighs so I don't know if he's grossed out or something. He always tells me how pretty I am and how much he loves me, but I'm worried that maybe he's not finding me attractive anymore....any suggestions?