Vaginal bleeding could mean ?

For the last few months I have been told that I had a UTI, even though the tests were negative. I’ve been put on amoxicillon, but it doesn’t seem to help. It burns when i go to the bathroom, and is unbearable after sex. I bleed, sometimes heavily, sometimes not. I’m not sure what to do. No one will listen to me at home, so i started some research on my own. I found an article on implantation bleeding. Now I am afraid I may be pregnant . . .