What is with my body ?

hello community, i got a big question. since beginning of the year i am trying to be in recovery. i started with 47kg and gained up to that 7(?) kg. but at first i just could eat 1 meal a day. sometimes it Was a really big meal, but i just Hit the 1000 calories a day; with luck. i try to get up of that, getting 3 meals a day. like i should. i tried this a whole week, but i gained 5 kg from that and my scale does not change. So i get here the question; did i really gained fat or weight that fast ? i am seeing ppl eating 3000 calories a day and not gaining weight that fast and i just eat up to 1000-1500 with all 3 meals; bc i cant because of my body( and kinda because of my head). or is this just fluid retention/water weight? i know i should eat but i am so in frustration. i feel like i am "getting bigger". my legs look like they gained so much fat; bc they r wobbly like my body. and i have to say here that i am very active; at day i get my 10.000-20.000 steps and also make Sport 4x a week. i dont understand that i know gaining weight should be the first priority but maybe someone can calm me down here. thank you