It sounds like you are in the range of "average", but even if you weren't, what good would it do you to hear about it? There isn't much that can be done about it anyway. Besides, most girls are less obsessed with size than males are.
If you are worried about a girl's reaction, just date her for a while before you become intimate. If she really cares about you, your size will NOT be the most important thing.
Relax... I'll need some information first. Just the basic facts - can you show me where it hurts?