Is there something wrong with me?

I have been having sex with my bf every weekend. He cums inside me all the times and we use no protection. Every two weeks I take a pregnancy test and they are all negative. There are days that I get pregnancy symptoms but when I take a pregnancy test they come out negative. I was recently bleeding for a whole week it was a very abnormal period. Can I still be pregnant? Is there something wrong that I can't get pregnant?