My weight, for some reason is low on Mondays, stays the same or even slightly increases throughout the weekdays, and then is down again the next Monday. Not sure why, but I’ve noticed that’s what happens. I would stop weighing everyday if it’s gonna upset you when you don’t lose each time. I just weigh a lot because I find it interesting.
You’re right, 4 days isn’t long enough for a trend. Two weeks is barely enough for a trend imo. Two months seems like a decent starting point.
Stop weighing every day and relax a bit! Weight can fluctuate up to 2kg a day for some people just due to water. You mentioned exercise/sports and “gaining”. Did you drink a lot of water? It’s likely you didn’t pee all of it out. Extended fasts can also lead to more water rente toon in between feeding windows. If you’re not eating, it’s likely that you’re filling your stomach with water instead.
I would switch to weighing once a week and adding a non-scale measurement. Maybe you have a pair of pants that is just barely too small? Take some pictures!
You got this! :)