Hello tabenda, welcome to Psych Central.

Pushing people away when they come on too strong or pushy sounds like a safety mechanism that you have learnt. It's possible that some sort of fear brings up this protection mode in you. Ultimately you would need to look into why you have this reaction each time, have you been hurt badly in the past? If you have been hurt badly in the past, it is a natural reaction. You can work on it if you are aware of it and have partners/friends you truly trust.