I can believe that you aren't depressed and don't need to see a doctor. Certainly, as that's how you see it, I think it's more useful to work from there.
Your posts say clever to me. You write short, yet well put and to the point sentences. You're lucid, able. I like your name too.
If you don't think you are depressed, I think you sound smart enough to be quite probably right.
Chronic procrastination? Boredom writ large, because the way things have panned out has seen you fall into a life with no major interests, good stuff happening, so you've lost interest in your own world?
It's easy to gain weight and go on gaining: hard to lose.
It's hard to make good friends when there's nothing for the friendships to 'hang' on. If you don't have interests, a pizazz about you, because you really aren't feeling it, people can tell, and they back off. Not because you're 'crap' so much as - it's more of a risk trying to friend up with someone who seems lukewarm. Most people are less confident inside than they might seem. And then you get the snowball effect - your birthday - 'ooof, well, will she really want to see me anyway? It's not as if we're super close or do much - oh I won't go'.
Solutions: I too would tackle weight first. Because it's not just 'weight' - losing weight, better nutrition and exercise, is all a massive mental boost and will improve your health and have a huge positive effect on your mood. But it's HARD. You have to see it as a long journey, not feel daunted by the whole job at once. I would focus on weight and health, and really use that clever brain of yours to tell yourself this has to get sorted, and work out the best way towards better health which WILL work for you. Classes? Swimming? Healthier eating that isn't a diet? Tiny changes will be easier and WILL work - over time. How about, say:
Until March, do the following:
- eat less wheat
- take carbs down a bit
- increase veg
- try your best to get to grips with the sugar addiction. Eat good fats instead of processed crap when you feel the binge urge. Have things like cheese and oatcakes to hand instead of choc and crisps.
- start some sort of exercise - a walk in the evening. Make it longer and faster.
You will see a difference.