Sentso

Sorry to hear it's so hard with your friends, but just prove them wrong!
You seem motivated. Maybe in a few weeks/months it's gonna be easier. Maybe seeing one person at a time instead of a group of people (were they in a bar?) would be easier.

Last time I went to a party without drinking (I wanted to try, and also I had been drinking way too much the whole week before), I kept drinking sparkling water and saying I was taking a break. And still a few people, either joking, or seriously tempting me, offered me some beer or a glass of wine.
And I know if I tell them I quit, some will make fun of me behind my back, simply believing it's not possible.