Ok so I was supposed to get my period about a week ago, but instead got a light brown discharge for 4 days. I waited a week to see if I was pregnant. I did a pregnancy test exactly a week after this weird period happened, and it came out negative. I was relieved because I didn't want to be pregnant, and figured that maybe it was normal to see a period that was only brown discharge, since my mom had this happen to her before as well. But just yesterday I had a bit of light brown discharge mixed with some normal vaginal fluid. I got weirded out but it went away, and now today I just noticed when I wiped myself in the bathroom, that I had some blood in it. I wiped a second time and more blood.
What is going on???
Also Ive noticed some weight gain (slow but steady, of about 0.2 to 0.4 gains each day) Its been a whole pound already.

Please help, Im really concerned.