seeing as you appear to be from the Montreal area, here's a more local-specific info: the quasi totality of games posted on ASC for Quebec are 18+. There are a few groups (on FB) that allow minors, although at least one is in very bad standing with the rest of the community (AisoftQc). So while you might be able to play with them, they may not be the best people to associate with; and the association with them may even come back to haunt you when you do turn 18. Not to mention they aren't exactly milsim -minded. (kudos to you for your interest in milsim, btw!)
The alternative is wait it out. You may be able to find some boot camps etc that allow 17 y.o. players (we did one a few years back with several 17 YOs), some organizers may allow you to play after that. If nothing else you'll get yourself known, earn the respect of the community for waiting and following the rules and I guarantee when you turn 18 you'll be welcomed warmly.
Depending on how serious you are about milsim, it's also a good opportunity to save up for gear and stuff.