Any more details? I do get red itchiness down there sometimes, but only usually after a week when it starts to grow back.
Maybe you didn't shave in the right direction. I've never been 'taught' how to shave, but we are suppose to shave in the opposite the direction in which the hair lies?
Possibly sensitive skin.
(Ok, I'll admit. I'm not an expert in this field, so maybe I shouldn't be giving my opinion, but I just thought it would be helpful).