that's not how it works. fast too long and your metabolism slows down to compensate for the lack of calories

You have to keep eating, but at the same time burn off more calories than you eat.

literally no matter your age and height 100# is borderline UNHEALTHY. You can't loose weight because you are already digesting your stored fat. this is called anorexia not fasting. I honestly suggest seeing a mental health professional

you would not gain 4 steady pounds from 1 weekend of cheat/eating. Your body would have to be exposed to the higher calorie exposure longer than 2 days. a lot of your excess calories would pass through for just a cheat day/weekend. and fasting like you mention would have more than made up for a short spurt. I agree that you likely need help for an eating disorder and are trying to justify it here.

One weekend would not make you gain 4lbs. A single pound requires 3000 extra calories, so unless you ate several entire wedding cakes during the weekend and downed them by chugging jars of nacho cheese, there's simply no way. Additionally, fasting is not the way to lose weight, because it puts your body in starvation mode, thinking that times are tough and it needs to conserve its strength. A million things can contribute to the scale showing you're 4lbs heavier. Water retention, whether you've used the bathroom or not, whether you've already eaten and have food in your system, and if you're a biological woman your hormones from your cycle can throw things wildly out of whack. And another thing, idk how tall you are or how old you are, but 103 doesn't sound like a healthy weight for anyone, unless you're 12 and 4'6. 106 is probably perfectly fine and healthy, if not too low, and if you truly do think otherwise then I agree with everyone else saying you should speak to a mental health professional about body dysmorphia.

if you're like under 5" then I feel for you. but if you're normal then boo hoo poor you. (sarcasm). get some kind of help.

Wow, and here I am at 320 pounds grateful for the progress I’ve made.

Oh, friend. I think you may benefit from seeing a therapist.

Why are you fasting when you’re already so thin?

A healthy cis\perisex female adult is supposed to be around 125-135 lbs. You are going to seriously injure yourself and you need to seek help for whatever the hell is making you think you're not thin enough. You are VERY underweight. I cannot emphasize enough how much this will injure you in the long term. Stop doing this and go seek help.