help in need of advice

My bf just told me that our sex has become boring and it definitely makes me feel sad. I feel like after I had our first baby and been on bc for the first time ever he's been more frustrated with me.I'm wondering if it's me or both of us or what. Idk what to do or how to fix it because I love him very much and been with him for almost 10 years. Could someone please lend out some advice please