Constant Bleeding for 3 Months, Is This Normal?

On my period right now, but I'm not sure I can even call it that. At this point I've been bleeding almost constantly for 3 months, called my GP after month 1 then month 2 and she basically said to stop wasting her time because I got the arm implant in July and it was probably just that messing with my periods. This can't be normal right? I feel so tired all the time and sick and when I stand up I get dizzy. No matter how much I sleep, I'm so so tired when I wake up. Eating has been hard recently, only been able to have one meal a day or if I try to have more I feel sick. Plus horrible cramps and migraines and I just don't know what to do anymore. Help?