The reason you can quit for a short time, but eventually slip, is because you have not dealt with your addiction properly. You’re what they call “white knuckling it” - basically avoiding alcohol out of sheer will. This always fails, especially during trigger times (stress, hanging out with the “old gang,” etc.)
You may not need in patient rehab, but you do need help. Start attending AA. Go every day for a month and see the difference. You can’t do this all alone by just trying to force it. It will not work, and your alcoholism will escalate. You do not need to be a falling-down sloppy, drunk at 9 AM fool to be an alcoholic. Many good, successful people suffer with the problem.
Maybe you are thinking that going to AA would be embarrassing. Maybe you are afraid you will see someone you know there (who, by the way, would be there for the same reason.) Maybe you think your problem isn’t bad enough to warrant something like AA. Maybe you are afraid you will be the lone person of class amongst a bunch of felonious drunks who are unlike you. These are things everyone worries about before they go. But, just do it. You will be in good company - little old ladies, doctors, lawyers, fathers, church pastors, at home moms, teenagers, business owners, and yes the bikers and repeat DUI offenders you imagine!
You’ve already taken the first step in admitting you have a problem with alcohol and are using it inappropriately. Good for you! Now, go handle this so that it doesn’t hold power over you anymore. You CAN do it. My dad has been sober 37 years and still goes to AA three days a week : )