How do I know when I'm cumming?

its almost the same feeling you get when you masturbate. The best way to come is for you to be on top and grind on him and ride him back and forth and once you feel that feeling you know you have an orgie and came.

If you came, you'd know. Most likely, being new to sex, you haven't come at all. See with boys they'll pretty much come at anything, I mean I can give a guy a hard on just by stroking his leg. It usually takes a girl awhile to be comfortable enough with sex to have an orgasm, it can take girls more than a year after losing their virginity to have one. If you are coming you'll probably feel so of out of control, it should just feel amazing, maybe a bit of tingling, I think it really depends.

You can tell when its an orgasm, its a more intense feeling than what you just get from penetration.

hmm... if you cum, you'll know it! it's REALLY rare for a girl to come the first few times she has sex, especially if there is nothing but penetration going on. my thought is that it just hasn't happened for you yet. it will, though, with time and practice. no worries, as long as you have fun.