What Causes Pain Inside Of Vagina?

hi doc, when i try to finger my girlfriend she has a sharp pain inside her vigina, i know im doing it right as we have played in this manner before and she was fine but these days the pains that she gets is stopping our shall i say fun, i just wanted to know what i might be doing wrong or if there is something wrong with her sexual organ, she also now complains that she cant put a tampon in as that has also now started to hurt is this normal ? .