From what age do you know if you are actually gay?

it depends on the individual. i was having oral with a friend from primary school when i was about 7-8 but didn't realise that it would lead to me liking cock for the rest of my life!

i didn't really realise until i was old enough to know wot homosexuality was and then realised that all those things i had done as a kid were acts of gay sex - ergo - i must be gay! Some people know they're 'different' and like members of their own gender at a very, very early age (me: age 5) even if they don't know learn about "gays" until years later. Others don't realize it until it's much later, maybe their 20's or 30's or 50's and suddenly BAM!! it dawns on them why they've been so unfulfilled in their up-to-then straight life.

So the simple answer to the question is that there is no specific age at which you're supposed to know, it's different for everybody.

Also, some people know and accept it right away (at whatever age they realize it) and others take eons to wrap their head around it and finally accept it - this would be in response to the "if you are actually gay" part of your question.