Matty well done on being so strong and focussed, and for coming right back here with your honesty.
Perhaps last night, meeting some new housemates, you just wanted them to see you as 'normal' just the same as your other housemates? People can make swift judgements when they meet someone new, an you say you were already being accused of being antisocial. I feel this was a case of not wanting roommates to form an opinion of you that is not totally true. Maybe you can just show them over the next few days that you are a fun guy to be around, you just prefer not to drink to be that way.
I have every faith you will do that