There are different things to try but the best thing to do is ask your dr. I know that probably isn’t the best or most helpful answer but its the safest. I am pretty sure I have an untreated eating disorder because I couldn’t get proper help managing my weight. (I have always had the fear that I didn’t weigh enough)

Definitely talk you your doctor, but if you can afford protein powder I sneak it into my day. My fave is Isopure. They make typical milkshake flavors but also clear fruit punch (it’s kind of bitter but not bad) so you can sip it all day. Also a plain unflavored kind you can put in cooking. It feels kind of like Parmesan cheese so I put it in spaghetti sauce and other recipes.

Eating a lot of protein and carbs is your best bet to gain simple weight. I’d go with something like a lot of rice and chicken with broccoli to gain weight healthily. You never want to just gain bad weight when you can do it healthily. If you’d like other options you can message me and I’ll find some things for you.

definetly consult your doctor! if thats too much or not an option use this equation (weight in kg)*(0.9 for female or 1.0 for male)*(24)*(1.2)=? and that'll be the minimum amount of calories you require in a day to maintain basic functions (Total Energy Expenditure), then I'd add maybe around 500-1000 extra calories. you don't want to add a ridiculous amount and overwhelm your body, but you want to make sure you're taking in more than you're burning. and you want to be in the recommended percentages that the FDA recommends for carbs, fats, and proteins (more towards the higher end for carbs) and this will help you maintain a balanced diet.