I missed my daughter's birthday?

Yesterday was my daughter's 6th birthday. I promised her i would be there even though her mother my EX wife Stacy and i don't get along. Anyway i dropped a friend off at a party and didn't want to go in but he convinced me telling me a friend who i had seen since high school was there so i went in. She was there and we started drinking. Eventually i got drunk and i woke up yesterday with a hangover and completely forgot it was her birthday. Stacy called me furious cussing me out telling me she was crying because daddy didn't show. I told her i was so sorry and vowed i would make it up to our daughter. I have never felt smaller in my entire life. I love my daughter she means the world to me now i feel like she can't trust me. Stacy reinforced her belief that I'm an alcoholic and i needed rehab. She told me she divorced me because she couldn't handle watching me drink my life away. I don't think I'm an alcoholic i like to have a drink once in a while but that's it. What should i do?