Help me


so two weeks before my period (feb11) so last week I had really bad lower back pain and lower abdominal pain I went to the doctor everything came back negative as if I was perfectly fine but I still have some lower back pain this week I had some boob soreness then discomfort in my lower back and abdominal I took a pregnancy test it came out negative but, today I have lower back and abdominal discomfort and I so tired, what could this be?