usually 3-4 months with no period, now i have 3 in 7 weeks?

Hi,
Welcome to ehealthforum,
The initial irregular periods could be attributed to anovulatory cycles (menstrual cycles without periodic egg release from ovary). PCOS also results in irregular periods. PCOS usually responds to treatment with insulin modifiers as most common cause for PCOS is insulin resistance. Consider discussing with your treating doctor/gynecologist about getting started on these along with hormonal contraceptives for better control of PCOS and for regularization of periods. The recent heavy bleeding, painful abdominal cramps, could suggest possibility of hormonal upset, ovarian cysts, endometrial hyperplasia, endometriosis, bleeding disorder, anemia etc. The exact cause can only be made out after careful evaluation. Consider visiting your doctor/gynecologist at the earliest for thorough examination and further evaluation to look for the underlying cause for the abnormal bleeding that you describe. Treatment as needed (based on examination findings and investigations results) would be started to help you control the bleeding and regulate your periods. Consider being in regular monitoring and follow-up with your treating doctor/gynecologist and report any new/abnormal symptoms immediately. Drink plenty of water. Take adequate rest. Maintain healthy diet and lifestyle.
Take care.