HELP!!!

I am 18 and I had my period 2 weeks ago but before that my boyfriend and I well you know we have sex a lot and I am on birth control the implant. Now I am spotting and I have been for 4 or 5 days now and I keep getting these cramps that are worse then period cramps. I am peeing a lot and eating all the time and tired plus having odd cravings. The implant makes pregnancy tests come up negative no matter what but I am scared to say something to my mom. I am on her Insurance and so she would have to be there for anything to happen. In the state I live in I cant go to the women center because I am not considered an adult til I am 19. This is also how my sister found out she was pregnant with my niece but she wasn’t on the implant. How do I tell my mom or even bring it up? Should I even be worried?