I had the same problem, but once you start a little forplay your mind usually switches in to sexy time mode! I just needed a little oomf to get me going then you get in the mood! Talk to him tho. Tell him your hormones are crazy right now! Communication is key!
I know it's not insecurity I just dont have the urge
try sexy outfits, i found while pregnant my insecurities were a big part of not wanting sex, even if you don't feel sexy, he will think you are, and it really helps! try going on dates, setting the mood for later, stuff like that!