I'm 11 and can't get sex out of my mind

Well, I'm 11 and can't get sex out of my head I try talking to my friends about it but they just laugh it off and stuff like that and I try humping a pillow but it doesn't work, it just doesn't feel good,what should I do to get it out of my mind,plz help

First) Your 11, which means you're probably going through puberty at the moment, so stop worrying. It's normal to think about sex a lot during that time, and there isn't really anything wrong with you thinking about it or being curious about it. Lots of people says stupid things like, "Your too young to think about that." but just ignore them, because they thought about the same things I'm sure. Just keep in mind that thinking about sex and having sexual feelings is natural. Maybe avoid actually doing sexual things, like if a guy in his 20's started trying to do things with you, but other than that you're fine.
Second) Try touching yourself or watching porn or something.

At your age there is nothing to worry about, you're not supposed to be trying to get it out of your head or off your mind because it is only a natural phase on your way to maturity that you are going through, if friends are laughing it off well maybe they haven't got to that point of transition yet, we are all individuals who mature and develop at different rates.

It is normal for you to be feeling horny and having the desire to relieve your sexual tension by experimenting sexually with an other person but until you have some knowledge of safe sex practices and basic sexual education and understanding the possible consequences of engaging in sexual activity with an other person, it might be a better idea to experiment with viewing porn as a way of release in combination with masturbation could be a more safe way for you to gain some understanding with the basic positions and mechanics of the sex acts themselves.
However keep in mind that porn is not reality and is basically for entertainment purposes.