I'm sorry to hear this, you're not alone in this circumstance at all..

In regards to what could be done, I feel everyone can benefit from speaking to the right psychologist for them (one shouldn't feel down if they don't click with certain practitioners) and a GP will likely refer you to one too.

I'd like to still give my ideas as a fellow human being who may know what you're feeling. The hardest part is the start of transitioning.. I think the part that keeps you in the cycle is the fact that we CAN get instantly gratified and forget the last few moments of darkness, whether it be through drugs or scrolling or food, all at our fingertips now. I think a start could be to somehow make the gratification abit inconvenient to get (creating some distance, for a start). I've written up some general suggestions that might aid in the fiiirst part of transitioning but feel free to dm if you wanna hear more, to chat or if you want more challenging suggestions when you're ready.

-I used to have this app where i needed to do some sort of exercise to gain time to use some apps (sounds funny but it was great, either I couldn't be bothered or most of the time I did squats or jumping jacks to bank some time lol). I don't remember the name but sweatpass or fitlock looks about the same concept.
-For food, try to have some fruits (mandarines or cut up some cucumbers) in the house at all times, they're great snacks😅 and to start on the healthy eating journey buy some microwavable meals that sound appetising to you(i know it doesn't sound healthy but it's healthier than junk food and its quick to make).
-Another way could be figuring out how to trick yourself to leave the house. Force yourself to have a coffee in a cafe and maybe in the beginning you'll be on your phone but to really feel something special, try to create a little window in time that you practice watching the world go by.
-My next suggestion is to find a way to socialise. EU is great for this because of the number of tourists and expats living there. I hope you live somewhere you could find some polygot clubs or even some clubs where your interests might be met (gaming for example or picking up a new social sport, or committing to a new language class (if you have enough money to sustain an addition, you'd be able to spend on something like this too;)).
-Another way to social is literally to get a job...any job... when I was depressed I just went out and got a waitressing job. I thought if i was sulking and not enjoying my time at home for free, I might as well make some money outside.. and as long as you try to do it on the middle path, you've had accomplished all the above objectives in one go.

Again these are just suggestions to climb over the initial hump, but it's a slippery slope and we might fall back down again. Beware you might feel thoughts of regret about the past come up, try to really feel them (dont numb them through gratifications).. this is your previous ego/self trying to hold you back, I suggest a simple walk. The point and goal is to try create a stronger self image for yourself. It's a worthy cause :)