Sex and attraction

So my whole pregnancy sex has felt pretty amazing whenever I had a good day with little morning sickness I was very attracted to my husband.
Tonight was the first night I felt nothing. We've been together for thirteen years, this is our first baby- and sure struggling through fertility treatments could sometimes make sex a chore, and sometimes put the pressure on to make it harder to orgasm. But tonight was different, I didn't have trouble finishing, I had trouble just trying to be attracted to my husband. 
He was doing all the things I usually like, lots of kissing and being tender and sweet and patient and I can appreciate those things mentally, but my heart just wasn't in it.
Things I have always taken for granted like his smell, or his touch, or taste, his breath on my skin- all the little things that add up to passion and sexiness, I wasn't feeling any of it. I felt like I was kidding a friend.  It scared me because I didn't realize hormones played such a big role in lust, I just thought I felt those things because I love him. Now I'm terrified those feelings won't ever come back after the baby is born. I never thought sex was such a big deal, and I knew low libido was a strong possibility, but not feeling attracted to the man I love is really difficult to deal with.