Hey, welcome!
Sounds like you know the deal, you can’t expect your bf to do this with you but it kinda sucks that he said he would and then isn’t! What’s your situation, do you live together? I’m wondering if it is an option for you to not be around him while he’s drinking, if you feel that would put your sobriety at risk, especially while you are just starting out.
It really helps me to think about the reasons why I don’t drink, what happens when I do. Spoiler alert, it’s super tragic. Find a hobby, go for a walk, get an way night and get up with the sun, fill your day… Just don’t have that first drink!
There is so much advice and support here and I’m sure you will find loads you can relate to. Search, read, reach out when you need to. This is a brilliant post with lots of info and advice which you might find helpful: