Welcome to SR Jade
I used to have problems with blackouts when I was a bit younger than you. It would be seemingly small amounts of spirits that did it to me, and like you I didn't throw up or feel drunk... though really I would have no idea because I couldn't remember anything. It's really scary going out and only remembering the first hour or so... Has this happened every time you've drunk for 3 years?
I'd recommend telling your doctor and seeing what he/she suggests, though I'd imagine if I told my doctor something like that he'd just tell me to stop drinking!
Have you tried getting help with quitting drinking before? It might be worth looking into some support. If you're anything like I was I'd suspect you'll be trying to figure out how you can carry on drinking without having any negative consequences, but unfortunately these things tend not to improve.
Glad you're here x