I have an idea...
I think the reason I "crash and purge" after a 5-day restriction is because I don't plan. I'm not a planner at almost anything in life. But if I tried to put effort into planning my calories I could safely follow it and have the energy to work out again. Or at least pick up swimming again. I think that when I feel strong enough to not eat, I hang on tight to it as long as I can without worrying about the warning bells going off (cravings for a binge) and having a safe exit strategy (transitioning back to solid foods). I think that's what tomorrow should be about for me. Making a rotating schedule of "safe foods" under a budget of calories (800, 1000 on work out days). and planning fun workouts or places to walk to. It'll give me something to do instead of curling up in bed fearing my next hunger pain.