It's terrifying coming clean to parents about alcoholism or substance abuse issues, but they will absolutely support you (99.99% of the time they will, depending on the parent; the 0.01 that refuse to have profound issues that needs to be dealt with as well, i.e. their own addiction, personality disorders, etc.—I only include this because it would be dishonest not to). When I told my mom that I (at 17) was definitely an alcoholic, she lost her shit and started screaming at me and crying and hitting me because she watched it destroy her mother. It's not exactly a happy moment but it's an honest one; it will be uncomfortable but it will also yield so much value for both you and your father

There is no way I could have gotten clean off of drugs and alcohol without my mom being there for me—whenever I needed her support—during these past ten years, which have cost me dearly and have been no more pleasant than a living death

Talk to your dad and talk to your doctor—find a program/system/treatment that works for you. Just because you're 18 doesn't mean you can't be an alcoholic. You also can't be a disappointment (this isn't your fault). All this means is that you have a lot to lose if you ignore your instincts about your drinking

I wish you the best my dude, don't hesitate to hit me up if you feel like it