I need help

I hate the way I am. I'm not in a relationship but have had 'encounters' with my coworker, and we are actual friends too we hang out n stuff. But she also has a bf.
I realize my flaws, I'm sacred of her leaving when she's done with me, I have a fear of letting go. And I get upset when I know she's with her bf and act immature and start a fight to get attention. It's hard admitting this, but I want to change it and need advice to be more self reliant.