I have been taking Loestrin 24 fe for about 8 months now and my body has gotten used to it. I had a bad sinus infection last week and was prescribed Amoxcillin TR 875 mg. I started Amoxcillin last Tuesday night. I started spotting this Saturday. I was wondering if the antibiotic is just completely cancelling out my birth control so my body thinks it s on it s period? I also had sex last monday and thought about implantation bleeding b/c I had that with my first child. Please let me know. Thanks!