Single for 2 years

March will be two years that I have been single. I want to date but every time I start talking to someone I start second guessing myself and eventually run them off. I was told in my last relationship I basically wasn’t good enough for anyone. Now every time I feel like I’m getting for feelings for someone I second guess myself and it all goes down the drain. I basically just feel like I’m going to be single for the rest of my life and there isn’t anyone out there for me.