Mostly urinary tract infection. It can lead to kidney infection so it is serious. You need antibiotics, see a gynaecologist to get a prescription. Until then drink a lot and pee a lot, it helps cleaning it a little.
They could be growing or you could be getting ready to be on your time of the month. Only wear a bra when necessary. Take it off when you sleep if you dont already.This could play a role in it. If you're menopausal or something you need to have a mammogram done.