What is your gut feeling on this???
The fact that you are asking on here makes me feel that you are not 100% sure and therefore you want to err on the side of caution but having had all these disappointments in the past you so want things to be right too.
Take things slowly, at a comfortable pace. If this man cares for you then he will appreciate your past is affecting you and accept things on your terms. You could both be a wonderful help to one another.
I feel for you I really do. About 8 years ago a pregnant teenage girl turned up on my mums doorstep looking for my dad (who had left some 15 years ago) it turned out my dad was her dad too after he had an affair with her mum and all that time she had been living in the next street. I was devastated, I thought I was his only daughter and that had meant something to me. We never asked for DNA, she looks a lot like me. I didn't want to hi-jack your thread, just let you know that I know how you feel about families being the most complicated things in the world.
Moving away from the relationship issue, but back to the fact that you are unable to find your real dad, could you perhaps seek some counselling? Someone who could help you put your thoughts and feelings into order?
:hug99: