I have bipolar - an actual mood disorder - and I find that my moods will be a lot more unstable if my blood sugars aren't right, so I would not be surprised.
We also see it in children who don't have that much of a filter - fussy when hungry, hyper when on too much sugar etc. Common knowledge, that one, I think.
Sounds plausible - hope you get your levels under control if that is the problem and that things improve in any case.
Fluctuating moods can be tiresome and difficult.
Both RE the diabetes, the moods and any stress, a walk would help a little bit, so that's somewhere to start - just 15 mins once or twice a day would be recommended for a start.
Good luck.