I Am 20 Year Old Height 172 Cm Weight 57

I am 20 year old height 172 cm weight 57 kgs(currently) , i lost 4 kgs in last 3 months iam trying tu put weight but not able to gain, i am feeling skinny pls suggest me something to gain healthy 10 kg weight. Some suggested to take non veg but iam a vegetarian. plz help me to get out of this situation.