Hey Gaz,
I can understand how you feel. Being on the receiving end of rejection and heartache on a consistent basis is never fun nor does it help the confidence within us. Unfortunately this is something we as emotional beings have to deal with, though some more frequently than others. My best advice is to stop seeking it. Let it come to you. Those who are meant to interact with you will naturally gravitate to you. It is then you can decide how best to proceed. Don't force it, let things naturally grow, while tending the gardening if there are possibilities there. As far as feeling like you're the problem I would recommend taking time to truly self reflect on yourself and your actions during your relationships and interaction with those where a relationship was possible. It's entirely possible that you aren't the issue and they simply didn't think they were in a good fit. But after your self reflection, if you find something that you believe you need to improve upon then take time to make those improvements. Eventually you'll find someone who is suited for you and things can take a turn for the better. I hope this helps. Take care!