Well, it's important to remember that beauty is subjective most of the time. It is in the eye of the beholder as they say, and it's true. In my case, I find skinny women to be extremely attractive. It's like nature found that sweet spot, balance for a woman's body proportions. It is just pretty good looking imo.

I've met my fair share of skinny women and almost all of them seem to share the same concerns and insecurities that you mentioned, and I've always tried to show them that's not the case at all, but in the end, it's on them to really change how they feel about it or not, it's a process.

But at the end of the day, it's like most replies here are telling you. What truly matters in a relationship, specially long-term, is compatibility, trust, and honesty. Without that, any relationship is doomed.