Help Me!!!!

In December AF came on the 2nd. Because my period is so regular I expected it to come around that same day in January. Well it actually came on the 29th of December which was about 4 days early for me. For the past few weeks. I have been nauseated, boobs hurt, urinating more than normal, nasty taste in my mouth...you name it!!. So on the 29th of January here comes AF again. Heavy as usual. But this time accompanied by painful cramps that i normally don't have. Took a pregnancy test before AF and it had a faint thin line that looks like an evap line. So i guess my question is if its not pregnancy...What is it??!!!