Bleeding problems

Hello everybody,

So, I've been debating posting on here for a while, but at this point I feel so hopeless and I am hoping somebody can help. Here's the deal... I have been bleeding for way too long. I started my period several months ago and it was normal, lasting 7 days and stopping. A week went by and everything was great until one day I started spotting. It was light, and my first reaction was to take a pregnancy test that came back negative. Through the whole next month I bled, anywhere from spotting to heavy bleeding. I went to the doctor very afraid and they did std tests to rule that out, all of which came back negative. After that everything stopped for two weeks and went back to seemingly normal, leaving me hoping for this being a one time occurance. Two weeks later I got my normal period again, and thought nothing of it. After one week off I started the whole process again and here I am 2 weeks in on the second round of what I hope isn't another month of bleeding. I have gone to the doctor again. They did a pelvic exam and a pap smear which came back negative. They also tested for anemia which was negative and did yet another pregnancy test which was also negative. The doctor essentially told me this whole thing is stress related, though I am not sure what would have me so stressed. They just me on birth control staring the week after what I assumed was my last period, and so far 3 weeks in it has done nothing. I am not sure when to go back to the doctor or if I even should. And I just wanted to hear suggestions or similar cases and their outcomes. Thank you so much for any help you can provide!