took my nuva ring out and i had un protected sex...

Hi,
Welcome to ehealthforum,
If you have not been regular with your Nuvaring use and have been sexually active without additional protection, then the abdominal cramps and light bleeding could suggest possibility of implantation and pregnancy. The bleeding could also be the withdrawal bleeding that occurs after removal of Nuvaring. The brown discharge could also indicate possibility of infection if associated with other symptoms like foul smell, irritation, discomfort, itching etc. Visit your doctor/gynecologist for further evaluation and assistance. If pregnancy is suspected, visit your doctor/gynecologist at the earliest for thorough examination (to confirm pregnancy related changes/signs in body) and blood/serum HCG level test (to confirm/rule out pregnancy accurately). If infection is suspected, vaginal swab/smear test done on the discharge would help to identify causative agent and get you started on appropriate treatment. Be in regular monitoring and follow-up of your treating doctor/gynecologist and report any new/abnormal symptoms immediately.
Take care.