Why does my weight fluctuate so much?

I would agree you shouldn't "take days off." I know I feel bloated when I eat too much food or I should say too much of the wrong kind of food. I am also a big promoter of "not drinking my calories."

My weight always fluctuates like that when I did several things. For instance, I would eat too little while exercising (cardio) - restricting my calories without figuring out my TDEE, lose a few pounds after a couple of weeks, and then gain it all back as soon as I went off the diet for a few days. This was probably the most vicious cycle, and I was stuck in it for a long time before I started strength training. Restrictions like that just about always seemed to lead me back to blowing my diet, or it took very little to blow it. It also went hand in hand with drinking - I love craft beer and would sample several new brews throughout the week, not accounting for alcohol calories. I've always considered myself a healthy eater - mostly- because I try to cook all of my own meals and avoid junk/processed food. But, it wasn't until I seriously started watching what I ate, weighing meals and counting all my calories, and cut out most of the booze, that my weight stabilized and I started losing fat. Second reason is water retention from eating out, drinking and weight lifting. I'd say food and spotty accountability combined with an improper intake was my biggest detriment. It's worth planning out a regime around your TDEE (which accounts for your activity level) and eating at a 5-15% reduction, and diligently recording all of it for a month to see how much your weight fluctuates. Don't eat back your exercise calories and limit alcohol/cheat food during this time to a few occasions. I'm willing to bet you will be able to draw some very useful conclusions