I bled after masturbation. Have I lost my virginity?

How old are you? And when was your last period?

I am 15 and had my first ever period on the 25th novemeber and finished on the 1st of December (2016). I havent had a period since so i thought i started yesterday when i saw blood in my pants (after i masturbated with the shower). But then i didnt see any blood today at all. So worried. X