Question about 18 and legal?

The age of consent is not 18 in all states. It is either 16 or 17 in most states - each state decides for themselves. Finding out what the age of consent is in your state and what the specific laws are is as simple as doing a google search. To answer what seems to be your main question though, *most* states have at least some sort of "close in age" exemption to their consent law, which makes an exception to the law when the difference between the two parties ages does not exceed a certain limit, even if one of them is above the age of consent and the other is below it. For example, a state might set their age of consent at 17 but have a 2-year close in age exemption. This means that if a 17 year old and a 16 year old want to have sex, it is not against the law even though the 16 year old is technically below the age of consent because they are less than 2 years apart in age. Again you should look up what your state's specific laws are. Although most states have such close in age exemptions, there are some that don't. I know for a fact that California, for example, sets their age of consent at 18 and does not have any close in age exemption. Thus, in California, it is technically illegal for a man who turned 18 yesterday to have sex with a woman who turns 18 next week, ridiculous as that is. You should always be aware of the specific laws of the state in which you are living or residing.

the age of consent is 17 in most states and 16 in others

you do not have to be 18 in any state

Who is going to know? Unless you go have sex in public not only get charges for that but even more :D

I believe that if there's more than a 5 year difference it's considered statutory rape.. But it depends where you live. But seriously I wouldn't be concerned about that.. It's a stupid law if you ask me.