Same thing happened to me but a little bit differently . I recently had to get my back lanced because i had an abscess on my back it had got really infected and the hole in my back was the size of a quarter. The doctors prescribed me Keflex , Bactrim & also a pain killer . I had to take Keflex for 10 days & I had to take Bactrim until the infection was cleared & my back was closed . I didn't get my peroid at all last month .