Missed period or pregnant?

I would say your chances of being pregnant are slim to none. You're irregular, on birth control, and he's done the snippety-snip. You could talk to a gynecologist about taking pills to regulate your cycle, so you are better able to gauge and control what's going on. And about the drinking, that's not healthy. If you drink because of stress then try to get something else to do when you're stressed. My uncle drank himself to death. You're young. You should have your whole life ahead of you. Good luck.