I'm using implanon birth control. Since taking an antibiotic I've been having a cycle every other week. Before this it's been 2 years. Shouldconcerned?

Yes. First of all, you shouldn't relay on Implanon being effective for birth control if you have been on an antibiotic. Your cycles should settle down a month or so after finishing your antibiotic, if it doesn't, or if you develop fever, pelvic pain, or additional bleeding see your doctor.