Hello and welcome to EmpowHer,
I'm so sorry to hear you're experiencing these symptoms. I am a bit unclear on the pattern of your menstrual cycle. Please be a bit more clear on the menstrual cycle you are experiencing and I'd love to give you helpful information.
Do you mean to say that you have had periods for the past 3 months? Or do you mean that you have been bleeding for 3 weeks straight?
In regards to having painful sex, if it is not related to vaginal dryness you may have a more serious problem such as in infection. I suggest that you see a gynecologist and get a pap smear.