My weight is holding me back!!!

I’m a 164cm 48.3kgs dude and it’s very tiring to say the least. The closest one to my weight class in the gym is around 60kgs so every time I spar it’s basically hell.

I’m trying to gain weight for a long time but I just can’t seem to hold the nutrients in my body.

Has anyone gone increased 6-7+ kgs while training MT? And how?