11d - I'm so sorry for how you're feeling! 17 years and 3 kids. That's a big history. Keep reading posts, find a naranon or alanon meeting(s), get some books (Melody Beattie!) You need to work on you!
My sex life was not good, from the beginning it wasn't great and it just got worse, so I went through the insecurity thing too. I went to therapy though (didn't know at the time I was married to an addict - and that's a side-effect of opiate addiction) but I started getting stronger in myself, and realized I was pretty enough, attractive enough, etc. If he wasn't interested, it was his deal not mine. I won't say I started strutting around or anything, but I did start feeling better about myself, and you know it made a difference for me outside my house. I made more friends, the kids in the neighborhood started walking with me when I walked my dog - before the kids said hi but didn't really seem to like to be with me. I thought that was a huge indication of how much better I felt inside - kids are a barometer! This is what helped me, I hope you find a way that helps you help yourself! You are worth it, I guarantee it!
Take care of yourself! Welcome!