I won't be a back up plan

About a week ago I found myself in the position where someone else was making a decision on my love life. I poured my heart out in a blog, about how I'd fallen for this guy, head over heels, and he had told me he had feelings for someone else and had to make the decision on who to stick with. After writing the blog about how  I couldn't walk away, he rang me within the hour to tell me he had been stupid to contemplate anyone else- it was me he loved. Within a week it has happened again. This time a married friend of his text to say her husband was moving out. So he informs me he needs some time again to think. I try pointing out how he is throwing something away for a fantasy, because at this stage she hasn't said she wants to start something with him, he is just hoping. In the end I started to loose my rag and forced the issue and he informed me he didn't want to see me again.
I was devastated. Part of me still is. Confused as to how someone can declare their love for you and tell their family about this new girlfriend (me ) and how wonderful she is, and then within 3 days bring it all crashing down. But the more I discuss it the more I come to realise its his loss. He is being stupid and will at some point wake up to that fact. If and when he does, I plan to have my head straight so I can see him and the situation for what it is. I wont be someones back up plan. I don't want to be standing in the wings ready to drop everything for him or anybody. Truth is if he saw how wonderful I was to start with he wouldn't have even contemplated these other women. You may believe the grass is greener on the other side or want your cake and eat it, but it rarely works. In his case my belief is that if he had liked her that much in the past when her marriage was failing, the fact that she was still married wouldn't have mattered.
So now I'm starting again. My barriers are raised slightly again so as to make sure I don't get taken for a fool so easily again. If he comes crawling back I honestly don't know how I would react at this point. I know I wont be deleting this post though!
New motto ' once written never deleted '