1 1/2 months late and now have a watery period

So I was 1 1/2 month late on my period the latest I have ever been b4 and now my period has come around but it is very different from what I'm used to having. Normally my blood is bright red and sometimes clumpy with a medium to heavy flow and I have terrible cramps along with nausea , sore nipples, and elevated body temp. This time around i already experienced the nausea and sore nipples the whole 2 weeks before my period. And one the first day I had seen red spots so I wiped some more and could see faint pink on the toilet paper so I went ahead and put a tampon in. Later on that night I check it and the tampon is covered in brown blood and even when I wipe it is brown whiched I figured it's because my period was so late so that wasn't alarming to me, what was is a some hours later not sure how many because I took a nap I can feel the weight of the tampon and when I went to check it I got watery blood all over my hand and the tampon was soaked and was watery pink and because of this I been having to change my tampons more often than I normally do because they be so soaked I cn feel the weight of it and I don't know what's going on with my body. 
Has anybody ever experienced this before? O and I took a pregnancy test and it was negative it has been a week now and I'm still debating if I should take another one or not