What is it??

My cycle ranges from 23-27 days but my last one has me worried....it was dark an brownish in color not heavy enough to soak a tampon it was like that for about three days. For about 3 more days it was light pink only wen I wipe. Since then I have gained 6-8 lbs. Took a test an it was negative but lately I have been extremely tired a feeling bloated. Also taking frequent trips to the bathroom. An my hormones has been ragging I want it everyday several times a day. Is this normal or pregnancy?