If I can get AIDS only by an infected person why it is said that u get it by just having sex with many people?

because you increase your odds of sleeping with an infected person when you sleep with allot of people. many people could be cerriers of the disease and show no symptoms for years, maybe never, but they can still pass it on to you.

If all the people you sleep with are HIV- then you will not get hiv. They say that because the more people u sleep with the higher your risk. On the downfall, you could be a virgin, have sex with a hiv+ person and end up with HIV. I know plenty of people that sleep around a lot and are still negative. But they say that to warn people. Kinda like the lottery, the more you play, the higher your chances are of winning, but someone who only bought one ticket can still win. Odd way of looking at it, but its the truth.

because there is a posibility that the one of that persons that you have sex with, have an AIDS...