That is true. However, that does not stop under 16's from having sex. If you are under 16 and want to have sex then make sure you know what youre going in to and use protection. You can get condoms, from healthcare professionals, for free from 13 (i think) but if you are under 16 then they usually ask questions to make sure you know what youre getting yourself into.
Yes it is true, 16 is the legal age of consent, however i would say that a large majority of people do have sex before they are 16.
I do think that once youre older than 13, as long as you're safe and you know what you're doing and youre mature enough to understand when someone gives consent then you shouldnt feel guilty about it of course.
The law isnt there to punish you, its there to keep you safe because most people under the age of 16 and pretty much all people under the age of 13 are not mature enough to make the decision to have sex with someone so someone might manipulate you into thinking you're giving consent when you dont actually want to.