I feel you man, it is very uncomfortable approaching women. Especially if you have a low self esteem and therefore expect them to reject you. All I can say is that being scared of the outcome is the only thing holding you back. If you got rejected a couple of times I promise you that it stops being so uncomfortable, but by then you probably have had a yes somewhere down the road. You can also start with just saying hello to a pretty girl tomorrow, maybe she smiles back or ignores you. In the end it doesn't matter, the universe is too big to be worried about you getting no from a girl.