Why Am I losing weight so fast?

So I (20F) started a new diet plan 8 days ago. My starting weight was 139, and my goal weight is 123-125. I know I was/am not overweight, but I know I look and feel better closer to those numbers (medium boned, 5’5”).

My diet plan has included zigzagging calories, which has always worked well for me. So M-F I eat between 1450-1500calories, and then on the weekends I eat 1750-1800 calories. I aim for >100g protein a day and >25g of fiber. I eat vegetables at least twice a day and have been including potatoes and oats in my meals as much as humanly possible to help with feeling satiated. I also put balsamic vinegar on my huge chicken salad that I have for lunch most days. I essentially have been “adding not restricting” the foods that I eat, and it has been working a little too well. I also workout 4-6 times a week, usually only 20-30 minutes each. It’s a mixture of body weight exercises, cardio, Pilates, etc. I’m also drinking a stupid amount of water.

Before starting this way of eating, I was definitely in a surplus, and I was eating a crapton of sodium and processed foods. I was putting on weight really fast (~4pounds a month) and decided I needed to get back on track. I would go to bed every night uncomfortable and bloated. It wasn’t that I was binging or anything, I would just snack all day on rubbish. I also wasn’t working out at all, except for a long walk I would go in most days, which I still do now.

My starting weight was 139, and then this morning my weight is 134.0. I’ve lost 5pounds in eight days. Is this bad? Should I be worried? Or is it all those peanut-butter crackers getting flushed outta my blood? Advice would be appreciated!

Also this is my first post, so if there’s a better sub for this question, let me know!! Thanks ;)