Over 3000 calories 1 day, next day under 500

I've been here for 6 months on MFP and have had great success, had no troubles losing 80 pounds (currently 160 lb, male 19yo, 5'11) and I have been trying to get into maintenance mode and it is extremely difficult! My maintenance is about 2400 calories a day, I've tried so hard to get up there but this is my situation….

One day I will be like OK i will eat 2400 calories, but end up going overboard and having eaten over 3000 or more…. then next day I am not even close to being hungry and eat very little… this has happened for over 2 weeks now…. My weight has been fluctuating from 160 to 170.. I know it's mostly water and the amount of carbs i've been eating but its so frustrating….. I've calculated my calories from last week and I was around -3500…. but this whole eating a lot one day and eating very little the next is driving me crazy!

Here's the calories from last week
Monday: Eating about 2366 calories
Tuesday: Eating about 72 calories (net- after gym)
Wednesday: Eating about 2550
Thursday: Eating about -131 calories (net - after the gym)
Friday: Eating about 5000 calories
Saturday: Eating about -566 calories (net- after gym)
Sunday: Eating about 4000 calories….

So if I calculated this from my TDEE I would have lost a pound… I don't really want that but I don't want to gain weight either or messing up my body…

Any advice?