How to feel sexy?

Hi guys, I need some advice here. So, I’m in a 5 months relationship and our sex life has always been great, BUT all my life I’ve always had body insecurities. I always tell him that I hate my body, but he always disagree’s with me but I can’t help but feel he might break up with me one day because I’m not “sexy” enough. I usually dress pretty tomboyish, but in bed I usually like to put on lingerie to feel sexy but it doesn’t really work out sometimes. So my question is, how do I feel sexy about myself in bed or just in general?