It makes sense that you would have some anxiety about entering a relationship when you've had a negative experience. I think it's be good if you took some time to reflect on why you're feeling insecure. That is internal, not something you can pin on another person (because they're not making you think those things). Fear of rejection is common and you can overcome it. Just try to focus on those fearful thoughts and think about where it's coming from. If you're in therapy, you can try to talk it through with them too.