When you (guys) masturbate, how long does it really take you before you ejaculate?
Depends. I've got some folks I have cybersex with, and it can take me 3 hours or more before I actually cum. (I also prefer using both hands to type, so it's tough to get down to business.) If I'm just tossing one off, I can finish in just a couple minutes. It depends on how much time I have, if I've gotta be somewhere, how horny I am, if I'm playing with someone online, and it's really hot, lots of different things. So I'd have to say anywhere from a minute to 5 hours.
one more thing, how can you last longer? I'm kind of worried as I don't want to be embarrased
Simple: Stop jerking off. If you feel like you're going to cum, stop. Start up again in a minute. Learn the sensations of your body, and learn when you're going to cum. I'm assuming you mean that you don't want to be embarrassed with someone else, not just masturbating. If you're embarrassing yourself because you cum too fast jerking off, you've got other problems. Learning to know your body, and knowing what triggers you to get off, will be a great first step. I know that if my gf plays with my nipples while I'm having sex with her, I'll cum almost instantly. It's a constant matter of smacking her hands away from my chest. Condoms can make me last a LONG time. Some positions make me shoot quicker. If I've jerked off that day, I'll take longer that night. If I've been drinking, that might make me take longer. Certain drugs can make you last longer, or make sensations stronger so you'll only last a minute. Prozac, for example, can make you take FOREVER to get off, if you do at all. It's really getting to know yourself. Also, try and play around with kegel exercises, or tantric "male multiple orgasm" techniques. They might not help you last longer, they're just fun.