light periods

Sarah
My period is extremely light, it's basically spotting. I am on birth control and have been for almost 9 months now. I am sexually active too but always use a condom. I also have a UTI at the moment, but I'm not sure that will affect it. 
My period has gone from spotting to light, back to spotting, and then back to light. I'm not sure if I'm just worrying for no reason or should be worried.