Hi guys

My male checkered garter is behaving weirdly; for the last couple of days he's been very apathetic (earlier today I thought he was dead! Picked him up and he was like frozen, wouldn't move for a couple of seconds!)
He was born in the beginning of May and was with me since early September. He's used to being handled, his tank is absolutely dry and not too moist and the heating mat is only on one side and he mainly lies on the other, colder side of the tank, so I doubt he's too warm or cold. I feed him fish once a week, every second week I put some Vitamin B, D, Calcium powder on it, which he has been eating just fine.
His feeding day is Monday and he obviously always gets less active towards the weekend, also I think he's about to shed; what's worrying me though is that he's defecating a lot, which is weird since he didn't eat since last Monday! Now he's lying in his tank and kinda looks flat.
Maybe he's better tomorrow and is really just shedding but I've never seen him like this before, so thought I'd better ask!

Hope you can help me!

Cheers,
Jackie