So to begin my period comes on 4 days early which is not normal for me, it either comes right on time or comes a day (two max) early. So i think to myself no biggie it’s probably due to stress. Well my period lasted 4 days then went away completely for 3 days and now I’m on my period again with cramping. Its not as heavy as my normal cycle but it’s also not normal. The color is bright red. What could this be??

PS: IM def not pregnant because i just had a knee surgery 5 days ago and of course they do a pregnancy test which came back negative so I’m a tad bit confused here. Please help me out with answers.