I wish I had some good advice on how to stop a bender but I can't think of anything specific that worked for me. But I feel for you because I used to drink the same way. I'd be sober for periods of time and then once I got going, I'd just keep it up until I ran out of steam. There were days I'd feel stuck in my place, unable to go out because I was drinking and the weather outside would be beautiful. But id keep my place very dark and venture out at night to get more liquor.
The way I'd usually stop drinking is I'd end up sleeping about 6 hours, long enough for my inebriation to pass and wake up feeling awfully sick. Id lay there for a few hours, tossing and turning, knowing that it was time to tough it out. When the sun came up, Id get up, finally eat some food, get some gatorade and take a very hot shower to get the blood flowing. Id stay up for as long as I could and then I'd take a marijuana edible and sleep again . It was hard but I couldn't fully stop until the inebriation had passed. If I woke up still drunk Id just keep drinking.
I hope you can find a way off the bender. Those days were awful and I am glad I decided to leave them behind. But I remember feeling like I couldn't stop drinking even when I wanted to so I feel for you man cause I know what thats like.