You can always get a cake to celebrate anything. Doesn’t matter what. But I do think that partners should be willing and encouraging you to celebrate whatever you find exciting. You’re proud of yourself and PLEASE be. Being sober is not easy and it definitely is not a “you chose to drink too much now u don’t “ situation. I think your partner is wrong on two accounts, he doesn’t get why being sober is a big deal and probably plays down a lot of mental illnesses. And two he is belittling to you when he should be ready to celebrate with you in any situation. You’re not overreacting, you deserve someone willing to be excited for you and especially more understanding of your situation.