i've been struggling with addiction for close to four years. i've never gone more than 5-6 weeks without giving in. I want to quit for good. How?

Hey bentorah,
You've made the first big step to change by coming to GYE, good job. I'd advise you to read the handbook, and browse the tools that are offered. I'm sure there's something that can help you.
Keep posting,
360gye

A key factor that helps me get through is to take it day-by-day alone, never focusing on the past and very rarely thinking about the long-term future. 
What i find helpful is to get in touch with people who experience(d) what you do and keep in contact with them. By doing so i think you will feel accountable for your actions to them and more of a reason to stop. Keeping busy helps me not think about shmutz so much. I've heard from around the forum that exercising helps

Welcome!!

Welcome! Read the handbook.  Keep posting.  Find what works.  Commit to do whatever it takes to stay sober.