I have had a different experience while taking Amoxicillin Clav for a sinus infection. I have always been very irregular with my periods from almost the beginning of my preteens. Frequently I will skip a whole month from period to period. I took birth control pills for a while to make me regular but they made me gain weight so I stopped and I had just gotten married and we were ready to try to have a baby. And that took 7 long years to have her. I took about 3 of the Amox (one every 12 hours) and almost immediately started to get a bad yeast infection which I couldn't stand, so I stopped taking it and my sinuses seemed to be getting better. Right after that I started my period after just having it 2 weeks ago. THIS HAS NEVER, EVER HAPPENED TO ME BEFORE. So, about a week went by and my daughter was getting sick and my sinus infection comes back, so I broke down a few days ago and started the Amox again that night and by the morning I had started my period AGAIN- and full flow everyday and it is now Tuesday. Usually, it's a lot lighter by my 3rd or 4th day. I'm scared that something might be wrong. I need to make an appt with my ob/gyn but her nearest office doesn't take my insurance- only her satellite office about 80 or 90 miles away takes my insurance. Just worried that I may be experiencing early menopause at 43 which I do not want! We were going to try one last time to have another baby. Just hoping this is a side effect from the Amox... and I'm not taking it anymore.