I'm 16 and had sex with a 15 year old?

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Right the age of consent is infact 16, but this does NOT mean you will be prosecuted for having consensual sex with a person under the age of 16. It is statutory rape if the girl is under 13.
Anyway this law is only in place to protect minors when needed, so it's easier to prosecute people if somebody has been raped. Since she was fully consenting and since you two are 16 and 15 nothing wrong has been done AT ALL. The police will only find out if someone tells (WHY WOULD THEY) and if they do
a) they will not care in the slightest, happens all the time, they know it's likely to be harmless
b) There is noway of proving it anyway (especially since she consented)

Go and search the law you'll see the other answers to this are very ignorant