Your clit gets big after sex cuz of the stimulation-the rubbing. It's just like a penis. When it gets touched it erects. As far as the pain, I guess its just really sensitive. I don't know. That happens to mine every once in awhile.

No actually your clit is swollen, it is either because of the type of condoms you are using (you may be allergic) or it could be a vaginal infection. Hope that helps