Hi Alex.
I know it can't have been easy for you to come forward with this, so well done for making a thread and at least making the effort to ask for some input.
I'm going to tell you what i think of all of this; but of course i'm not a medical professional by any means so my opinion to you is probably worthless but here goes...
It just seems as though you are aware of your poor eating habits but aren't really bothered by them, which to me says you need a bit of a wake-up call. I don't mean to be harsh but being underweight can lead to very serious health problems if this isn't natural for you to be so.
You say you feel bad being ill and thin; well this should motivate you to want to eat properly, no? If not...then seriously you DO need some extra help from either a counsellor or a doctor. It is not normal to eat so poorly and become underweight. You should want to be healthy right? Being healthy means eating a balanced diet. There is no excuse for being lazy when it comes to eating as we humans need food as our fuel; without it we'll be weak and lethargic and eventually die. I'm sure that's not something you want to happen to you, right?
There are plenty of meals you can cook for yourself which AREN'T time consuming at all. For example stir-frys, omelettes, wraps(can be eaten hot or cold), pasta, etc. I think you need to learn that cooking meals and eating CAN be fun again. You get to add your own ingredients so you know exactly what is going into your meal - it's just great, and a nice way to become more independent, and you'll feel really proud and happy with yourself after witnessing the outcomes of your meals
Why not cook with some friends? It can be a good hobby to take up, actually. There are so many delicious recipes out there to try, you need to excite your tastebuds is all =]
I hope everything goes well for you.
Take care x