Why am I always second best?

My ex called and we talked and the main thing I garnered from the conversation was that he wanted to get back together. We’d been talking on and off and texting and it’s been good. When the pressure’s off, we actually have a good ‘relationship.’ After we broke up, he started seeing someone but he hurt her and she decided she didn’t want anything to do with him. That’s why he wanted to get back together. I was so happy to hear from him and that he wanted to be with me but then I realised that the only reason he came running back was because she didn’t want him. He told me once before that she made him happier than me. I told him how I loved him and got a very lacklustre reply in return. Why am I second best? Even though a part of me wants to be with him, I have enough self-respect to not be second best to anyone and be used this way.

My first ‘love’ didn’t want me either at first. I remember we had a really good relationship but he never looked and treated me the same as the ‘pretty’ girls. He told me he didn’t think of me in that way. He then got turned down by other girls and then told me 3 years later that he wanted to be with me. If he had found anyone ‘better’ he wouldn’t have even thought of me. So here is another example of why I am second best.

What is wrong with me? Why am I never anyone’s first choice? Why am I always the second option? I want to be with someone who feels that they are with me because they want to be with me. Not because nothing better came along or as a last resort. Is that unreasonable? Should I just be happy that someone wants to be with me? And not ask for too much.