Former D3 runner here -- here's what you need to do.
Stop drinking entirely.
Eat less, and eat better.
Start running doubles now. Get out the door for 15 minutes twice a day. Run as slowly as possible; you'll find it to be fast enough. Increase the time as you feel able to do so until you're running 60 minutes a day -- 30/30, 20/40, 15/45 60/0 -- it doesn't matter. If you keep almost all of the running quite slow, you'll be able to get there in 6-10 weeks.
Along the way, you should see some weight come off. I suggest you weigh your fat ass every day, but designate, say, Monday as the official weigh-in. By weighing yourself every day, you'll take heart every time you see that you're down a half-pound.
Weight loss will happen in fits and starts. Some of it may be so-called "water weight" -- that's fine, because it's still weight that you don't want to carry around.
Don't worry about speed or anything else for some months. At your age, you can get that back fairly quickly. For now, you want to focus entirely on dropping weight and rebuilding your base. However, it probably wouldn't hurt to do some strides a few times a week, say 5 x 20 seconds faster than you usually run. This will help your legs get working again.
As for getting your head back in shape, you need to commit to doing this for six weeks. If you can do that, you can get all the way back.