I think the first thing to consider is why you're dissatisfied. Is it because your life doesn't suit you or because your life doesn't suit what other people tell you should suit you?
Take me, for example. I'm in a very similar situation to you, although I'm a bit older and I haven't been on holiday for almost 40 years. Other than that, pretty much the same. In the past it bothered me to some extent, but I realised that was because of what other people wanted, not because of what I wanted. I don't conform to what they want for themselves. I realised that's not my problem. If they don't understand, that's their problem. My only regret is that my donor registration will probably be useless because I will probably die on my own and therefore none of the potentially reusable parts will be reusable. Transplants are only possible when someone dies on life support in hospital - the parts have to be functioning to be reused. Mine will probably be downright rotten before anyone notices I'm dead because it will probably be the smell of my rotting corpse that tips people off to my death. A shame for whoever has to clean up afterwards.
Anyway...
If it's genuinely the case that you're dissatified with your lifestyle, you have to change something about it. A good approach would be a hobby. Find something you find interesting. If there's
nothing you find interesting, it might be worth seeking medical advice about depression because everyone should find something interesting. It doesn't matter what it is, what matters is that it interests you. Painting, pottery, ancient Greek poetry, carpentry, rock climbing, Klingon, whatever. Not as a means of making friends, but as a thing in itself. You may well also make friends with people you meet with the same interest, but that's not the point. The thing itself must interest you because your life is about you, not about other people.
I haven't been on holiday for 4 years due to illness and having no-one to go with.
Unless your illness is one that means you require a carer, having no-one to go with is irrelevant. You're an adult. You can go on holiday without a parent or guardian.