Hey Joanna,
You seem like an amazing person, who’s like all of us here are trying to better our lives. As a guy, who’s been with so many women, I can easily tell you that he did not just text you saying “it was nice and he had a good time”, he actually enjoyed it or at least meant what he said at the moment. I really think you are over analyzing and be way too hard on yourself. Just relax. Take a deep breath. Meditate. Try yoga. Meet new people. I assume that since you claim to have such a low self esteem, that you don’t go out much. You’re already fine the way you are, you just have to realize this yourself.