OMG girls like you drive a guy up the wall! I'm dealing with one like you right now... It's very trying, to say the least... Things look good, you feel a connection, and BAM she avoids you and you're left wondering WTF just happened.
A good guy will not lose interest in you if you do something wrong. And he certainly won't point it out. He's not thinking "she likes me, but she's bad at flirting", he's trying to figure out if you like him in the first place. At most he'll simply be confused as to whether or not you're interested.
Even if you're scared, try to spend time with him. The kind of guy who will take the time to get to know you and break your shyness is also the type to get his feelings hurt if you avoid and reject him. Believe me on that one... :(
You've got to learn to control your "fight or flight" reflex. Running away is definitely easier, and I know - I used to be really shy too. But running away is NEVER better. But trust me, when a guy's asking to get to know you, he's outside of HIS comfort zone too, however good he may be at hiding it.
Also, you gotta learn to laugh at yourself. If you DO say or do something stupid, you need to laugh it off. Sulking because you made a fool of yourself will only make things worse, but if you laugh he won't think anything of it.