Is there a way out of losing interest in science during a PhD?
You show strong signs of burn-out. It is unclear whether you really lost interest in science or you simply did not make the proper transition from being motivated by the triggers of your youth (winning competitions) to the triggers of scientific endeavour on its own.
Also note, competitions are fun, because they are hard, but solvable in limited time. Full Metal Science, however, is tough. You have no idea whether things work, whether there is a solution and, if there is, how long it takes. It's a completely different game. It's a 100-m sprint vs. a marathon.
There are a couple of ways out. If you can afford to, you should take time off for a few months, even half a year and do other things. Stuff you enjoy, sleeping, traveling, gaming, whatever, without pressure. Forget science for that period. Then, but only then, after your return, come back and take account of what really makes you tick. What is it that you would like to be doing for the next 5 years? Not your lifetime, just 5 years. And move from there.
If you cannot afford to go away for a few months, there is something else you could try, namely starting a scientific hobby. Take a bit of time apart where you do something that is PhD-irrelevant. Solving problems? Hacking some software? Or something entirely different. Make yourself clear that this does not have to be published, it's just something to keep you aware about what you enjoyed about science. There is Feynman's anecdote about the wobbling plate, very pertinent to you. In any case, absolutely make sure to hard-limit your PhD hours per day. Make sure you keep a hobby, and a network of people etc. It sounds like a waste of time, but it isn't. Your other hours will count more if they are boxed in.
TL;DR:

Take time off.
If not possible, find a scientific hobby and hard-box your PhD hours.
Keep your other activities on plan, almost without exception (except for isolated important deadlines).

PS: I have no advice concerning your mentioning of hypersensitivity concerning feedback from others. That's not really a question we can answer here, and some people's advice would be almost automatically to recommend therapy. I am not saying this is not the right step, but some people find this overkill. If validation of others plays a bigger role for you than the topic itself, you probably need to consider activities which get you this validation more directly by interacting with people, such as blogging, science journalism (if science interests you at all anymore, that is).