Those sound like great things to make a person feel better! Pudding, reading, and getting to work on something you really want to.
I'm glad you're feeling better, and I hope at this moment you are STILL feeling well and happy.

Of course you exist, you're freaking awesome!~
You're not at all a waste of space.. why do you think that?

Hmmm, those are interesting questions.
Id like to thank you for sharing such candid personal topics online (in a public space).
What follows is a novel I've written in response (you've all been warned, Im a trained writer rofl)

My first reaction is to ask why you'd ask such existential questions: what prompted you to ask?
Some life event? Something someone said? Im fascinated as I observe a lot of people recently are asking similar questions. I'd suggest perspective and that sometimes people make opinions based on hypocritical standpoints/they can lie.

After that knee jerk reaction, and recalling I'm a writer not a doctor or therapist nor a lifecoach
it seems you might be suffering from "Comparison Anxiety", "Unfreedom of Overchoice" or "Uni-itis"*,
Comparison Anxiety/Uni-itis are common afflictions with youth and students (and can recur throughout life when changes/crisis happen) which is a condition whereby you make apples and oranges comparisons between yourself and others. These comparisons are often based on skewed data, perceptions and assumptions, and trends which are purely hypothetical/theoretical in nature. In the case of Comparison Anxiety, its that sense of being left behind, with uni-itis (or work based performance anxiety) its the cognitive dissonance that arises when you compare the task at hand with possible other tasks which you'd rather be doing instead.

Unfreedom of overchoice is a little harder to explain, suffice to say that past a certain number of options with particular constraints (such as a timelimit or resource availability), general human tendency is to not make any choices or make poor choices.

Tangent aside,
No one else is exactly like you; people (others, or "not you"s if you like) are just a spirit guide on your journey, where ever that journey may lead. Kindred spirits might walk together for a time, but sometimes paths diverge and take us to new places (and if we get lost, we can follow the footprints).

To borrow from D&D, you're on a quest, to find your passions - to find out who you are. Several destinies/passions do exist, such as "Find my destiny" or "Aid another in reaching their destiny" and the goldie
"Unknown Destiny/Passion" but more on that later...

I would say you definitely exist, at least on an interwebs scale! Look at all the artworks, look at the progress in your skills, and your innovative scroll technique. Maybe compare the total output calendar year on year and see how much more you're producing now compared to before?

If you're looking for real world stuff (friendship, intimate companionship, recognition etc) I'd offer the following advice, and this may sound bombastic, maybe try joining a volunteer organization, study (Arts, Sociology or Politics are fairly adaptable and broad, perhaps maybe something outside your existing skillset?), a new workplace/more hours at the job, a gym or a real world writers club/fanclub (often found at conventions or libraries) or something - something where you can put your array of skills to the test and get them recognised. If you're at liberty, the choice is yours.

The waste of space thing is an altogether more subjective term; it plays into that "comparison anxiety" thing I waffled about above. Waste of space, also known as regret, internal struggle, remorse or zugzwang (if you're into chess), I suspect is that feeling arising from a sense of relative lack of progress - a lack of choices made/things to show for it or remorse over being unable to make certain choices.
This is where theology, science, politics and philosophy would kick in to try and answer this question - all of which would suggest that you are here, and that you very much are not a waste of space/resources.

Conversely, politics and philosophy suggest you are alive, and represent an investment (Kropotkin, Keynes, Compatibalism/Communitarianism to name but a few) - both a self investment and a societal investment.
Also, philosophy (Locke, Kropotkin, Schopenhauer, Hobbes, Kant) suggests that you have knowable destinies and unknowable destinies, and consequently potentially many unknown purposes just waiting for you to discover them. (Note I omitted psychology influences, but Mazlow, Shrodinger, Kubler-Ross and Freud/Jung might be fun reading)

Theology or more broadly Belief Paradigms (especially agnosticism, Buddhism or pluralistic polytheism) suggests all of the above, and that not only is everything predetermined but that there might be a plan for you: something/s looking out for you.

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Anywho, I hope all of this rambling is of some use to you,
its not proscriptive so much as a rough guide: the questions you ask are so broad and with many answers (as "I" "Exist" "Waste" and "space" are such broad concepts .
Im sure that your art will be all the richer from these inquiries
Good luck

Yes and no....but mainly no.