I've been sober over six years now and still get irritable. It's part of life.
It can be tough any time, especially in early sobriety.
I've thought of making deadlines for sobriety, too. Five years was one of them.
But luckily my rational brain kicked in and played the tape back from the misery of my alcoholism. I never drank except for one reason-to get drunk.
And drink I did. I was a bad drunk and will be a bad drunk if I ever take another drink.
As for the caffeine, I drank pots of it after stopping. I still drink a lot of coffee.
I like it. It won't make me miserable. I won't lose my job over it. I don't wake up hung over.
I've moderated it somewhat, but I still enjoy it.
Anyway, hang in there. Things will straighten themselves out.
As my therapist once told me when I was depressed, he said 'maybe you don't have anything to be happy about' regarding my mental illness. And he was right.
Life didn't turn all flowers and puppy dogs once I quit. Life happens. Sometimes there are things to be irritable or depressed about.
Hang in there. It will get better and there's nothing that taking a drink will help.
Best to you.