Why do you think you’re so skinny? Do you not have a good appetite? Are you very active and not taking in enough calories to compensate (as I recall you have a broken ankle right now so I imagine that’s not it!)? Or is it maybe genetic? Is your mum really skinny too?
I have the same problem. Part of it for me is because of health problems, which is unavoidable, part of it is genetic, which is unavoidable, but part of it is because I have a crummy appetite, which is treatable. I take a pediatric appetite stimulant called periactin. It’s just an antihistamine and there are no side effects. Of course I don’t recommend medicating unless it’s a real problem.
Weight bearing exercise is a good suggestion, if you’re able to do that right now.
Mainly you’ll just have to eat more. Avacadoes are a good suggestion. Olive oil too is a nice healthy fat. And listen to your cravings. I think it’s just about impossible to gain weight if you don’t do that. A donut now and then really isn’t that bad for you, especially when you’re trying to gain.
It’s tricky because most people are trying to do the opposite and so all the so-called “health tips” you’re being bombarded with all the time aren’t actually healthy for you.