OP what do you not eat, I think I recall you saying you don't eat meat or eggs much. That makes it v. difficult if you're lactose intolerant as well. Tbh I know this probably isn't what you want to hear but I'd look at increasing meat/egg intake even if you don't like them.
I see you eat salmon, tinned mackerel is v. cheap, tasty and high in calories, protein and good fats. Same w/ sardines & pilchards but they are not as tasty.
Re: anxiety & appetite, I had the same problem as you & was underweight & I would just say eat through the pain barrier no matter how hard you find it. Even if it's just a mouthful. Then try to increase that gradually. You will get to a point where you will feel hungry every few hours anyway and it will come naturally to you.
I don't know if you drink or smoke but if so, stop. & I don't know if there's any science behind it but green tea seems to increase my appetite.