My 24 year old husband no longer wants sex! Why?

I've noticed that with in the past 4 months when ever I try to initiate sex he declines. We didn't even have sex on Valentine Day! We gave each other gifts and that was it. No dinner, no movie, no other plans. Should I be worried?

I have noticed all of the comments I must add that I have talked to him in the past when I noticed it had been weeks since we had sex. When I did ask, he said he was not interested or didn't feel like having sex. I tried to spice things up because I thought he was bored with me. He thought it was weird.