first period after losing virginity

KJM • Hospitality Industry Professional, Mom of One, Still Figuring Out Life
No one had any help before so here goes.
I lost my virginity a couple weeks ago & had sex twice since then but NONE in the past week.. I just started my period yesterday & it's not normal. It's normally a typical red color & pretty light. Instead it's lighter than normal & EXTREMELY dar like it doesnt even look red it's basically all dark brown. 
Why is this? Usually it's just supposed to be brown at the end not throughout your period.