I'd say yes, it counts as losing your virginity. The dictionary definition of virgin, one that people generally think of anyway, is a woman who has never had sexual intercourse... and here's the definition of 'sexual intercourse': "1 : heterosexual intercourse involving penetration of the vagina by the penis : COITUS
2 : intercourse involving genital contact between individuals other than penetration of the vagina by the penis." So technically, you're no longer a virgin. I do think it's kinda open to interpretation still though. Do you think you lost your virginity?

And my question is, what exactly constitutes "having sex?" Even looking at the definition of sexual intercourse leaves room for interpretation in my opinion...