sex rejection from your husband

my husband & I have been together for almost 5 years. we just recently got married in June of this year. when we first got together we had sex multiple times a day. now we have sex on average once a month. I know that the longer you're together the sex kind of falls to the way side. but we've been actively trying to have a baby since April 2017. it's difficult to try and conceive when you're only having sex once a month. but it's not even just about conceiving. I'm in general a very sexual person and would have sex everyday if i could. there are times I try and he says "he's not in the mood-tomorrow". Then i lay in bed unable to sleep because all that is running through my head is negative thoughts like why my husband doesn't want to have sex anymore, what I'm doing wrong, am I not attractive to him anymore, etc. any advice would be great. does anyone else ever have these feelings?