Or at least buy a freckling salad from KFC instead of the fried chicken in batter in bread. It won't be the best salad but it'll probably mess you up less.
About cycling every day... I ride most days (health reasons) for years now, but often it's 6 miles to shops and back or doctor's and back. I try to avoid going from zero for days to a 30+ mile ride because it tires me out more, but it doesn't always work out like that of course. I think I'd only sustain 30+ mile days in a row if I wasn't doing anything else - not work, not household tasks, not study, nothing.
Could you try starting off with a few less mammoth rides when you next feel ready?
You may have a point there, when I was managing 30+ miles aday last summer I wasn't doing anything else, no work, no college, no other extra stress, come to think of it I started having issues with fatigue the same month I started college? (September) ....interesting! Training stress+plus external stress+poor nutrition = Overtraining symptoms maybe?...I will cool down the long rides and keep to shorter rides once I'm over this.
Before you talk yourself into being mentally ill remember that depression is a symptom of overtraining not the other way round.
As for the diet you should obviously cut out the late night takeaway and what you yourself are calling crap. Overeating can be another symptom of doing too much.
Yeah I was anxiety and depression prone before I started Cycling (plus a few other issues), but that turned around dramatically once I started Cycling regularly, pretty commonplace to feel a hell of alot better once people incorporate regular exercise into their daily lives (switching focus to positives, less time to dwell on negatives) I was feeling pretty good with my new found passion. Pretty sure this downfall in mood is to do with Overtraining, shortly after and days following a ride I feel depleated of energy, hormones, the right balance of neurotransmitters (OK I don't know if this is true but I get this feeling), brain fog, insecure, unsure of myself and what's happing to me, feel pretty awful! Hoping once I'm over this and had a rest I should start feeling some normality return! Today is day 5 off the bike and I'm feeling a little better again, just need to have a break until I can confidently say I won't feel awful Cycling most days of the week again.
Also I rarely ate takeaways/junk food when I was Cycling regularly most days, I avoided it because it seemed counterintuitive Cycling hours, putting in the effort wanting to lose weight and get fitter to cancel it out with rubbish food, it was only when I started feeling like crap with long breaks off the bike inactive I would crave sugar, fat, sweets, junk food etc, like you say a symptom of doing too much.