Maybe my first period not sure?

Well I'm 13 1/2 i have had vagina discharge for 2 1/2 years and today when I went to the washroom when I wiped under there" this brown liquid it looked kinda like discharge I put a tampon in and when i took the tube applicator out it was somewhat Bloody on the rim. Could this be my first period?? What should I expect if this is my period?? By the way I am around 5 feet tall And 88 pounds full pubic and underarm hair and my breasts are " slowly" growing I'm about a size 32A and usually a 34A depending on brand Please help me out