I usually start my period around the 3rd of the month, I started Feb. 3rd and in March I started on the 5th. Now its the 31st  of March and i have cramps, which i expected because I should be starting my period soon in April but when I went to the restroom i was bleeding. I put on a tampon, the flow was lighter than usual but still red, now it is completely brown. I wonder if this is old blood from my last cycle or if it is implantation bleeding. I had sex a few weeks ago but we used protection and there were no traces of sperm anywhere but the inside of the condom. I have had no symptoms of pregnancy and i googled this "spotting before period" and all the results say implantation bleeding. im really nervous now and i hope my period continues regularly. Ive been really stressed since the day I had sex, even though we were protected i stress myself out everyday by over thinking and waiting for my period to finally come.  I would love to have your opinion on what this could mean. thank you so much