Pregnancy Test Being Negative But Have Syptoms

I'm a week late on my period. Took 4 pregnancy test at home and 3 came out negative and the other have a faint plus sign. Then also went to the hospital which was also negative. But I seem to have somewhat of the syptoms. Especially my boobs! They're so tender and sore, Headaches, naseua, dizzines, tired, cravings. What Could Possibly Be Happening?