How to gain weight!

I have been loosing lots of weight, i have cut on lots of sugar and meats i eat more veggies and soups than anything else but i do not want to keep loosing weight.. i do eat meat like 2-3 times a week tho, i just do not know why i loose weight, i have a very fast metabolism... maybe due to the greens i eat (fiber). Im 5’4 used to weight 123 last year... im 112 now.. soo low for my preference.

I did use to work out, but i stoped.

Oh i don’t consume lots of dairy since milk gives me stomach aches, i sometimes drink almonf milk. I eat 2-3 times a day!

What could help to gain weight?