I hope you take my comments in the spirit they are meant.
You didn't want to go to a wedding where there would be alcohol and you were anxious. You didn'tn want to say no to your partner and his family so went and had a drink.
On day 1 you went for a meal where there was alcohol and you were offered it. You did great saying no but putting ourselves in these situations really early on is definitely not something I could do.
Even if I didn't drink just being around it and being tempted by it so early on is just too challenging and unnecessary. I have learned how to say no to invites and that I am allowed to put myself first.
It's great your partner and his family like and accept you but please put yourself and your needs first.