Boyfriend not interested in sex anymore

We've been together for nearly 4 years now and in the begining sex was amazing but now if I even try to initiate I get turned down. I've tried buying new sexy outfits and other fun things but I get turned down and just feel embarrassed and kind of unattractive.

We only have sex when he wants and that is about once a month

I've tried talking to him about it, telling him how it makes me feel but nothing really changes.

Other aspects of our relationship is great. We talk we laugh we kiss we hold hands

Maybe he just doesnt see me that way anymore