<human>: Can you summarize the given text in a few sentences?

Throwaway so I can be more honest about the situation than I would be on my normal account. Long story short, I'm still hopelessly interested in someone I never even dated. We had a flirtation and hooked up a few times, but we're not in touch anymore and he has a serious girlfriend. But he's constantly on my mind, even though I actively try to focus on other things. I am in so much pain all the time whenever I think of him with this girl. 

I just want to move on. I hate feeling like this. I've tried dating other people and it just doesn't work. I still think how I don't care about them as much as I care about him, I'm not nearly as attracted to them as I am to him... etc. I am afraid I'm going to be alone forever because no one will ever measure up.

I welcome your advice. Please know that I cannot afford therapy right now, although that is something I have considered and would like to do as soon as I can.
<bot>: still not over an old fling, who has a serious girlfriend now. Can't move on no matter how hard I try... help :(