My two handed skill is currently at 38, but on the skill menu it is currently coloured in red and at 25.

I'm not poisoned, I don't have a disease, and I dont have any active effects lowering my two handed skill.

What gives? How do I find out why it's decreased?

Thanks for any help anyone can give. I will go [censored] insane if this is a game-ending glitch

(on 360 version)

I don't know how to check yet what poisons/spells/curses are affecting me... but it sounds like Oblivion where you need a "restore" potion. Also, try going to a temple and praying... that usually refreshes everything too.

What's the easiest temple to get to

I have been to a temple and still the stat decrease is still there

This is [censored] ridiculous