pain/discomfort is usually a sign of something wrong. she might want to see a doctor *could be anything from a hormonal shift to a yeast infection to STI to some weird food allergies - vags have a lot in common with women, they are cranky and never tell you what's wrong.*
in the mean time, if you both use lube switch to a brand with no glycerin. water based, non-gly lubes are kinder to her vaginal PH.
on the subject of lube, if you ain't using any you might want to start. see above for types to buy. KY is horrible stuff, spend a bit extra to get quality lube.
if you have recently switched condoms check the ingrediants on the lube, lots of women have sensitivites to Nonoxynol-9.
while you're checking condoms, see what else has changed since the problem started. laundry soap, fabric softener, body wash, perfumes, lotions.
either one of you can pick up a vaginal PH testing kit. easy to use, easy to read.
last lil bit. make sure anything you stick in her vagina is clean. wash up before you get dirty. small amounts of bacteria can cause big problems pretty quick.
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