I've been on 1,000 mg of metformin for 3 months now. I have lost almost 30 lbs and my periods were becoming regular again, every three weeks to be exact. Now it has been 5 weeks and 2 days since my last period. I have been sick and on antibiotics for the past 2 weeks. I have taken 2 hpt and both were negative. I'm becoming very discouraged at this point. I was so regular and now it's prolonged. Any advice?