I fought the spider in bleak falls and he poisoned me I think. My archery soil was 25, but te number was red and lowered to 20. For the life of me I could not find what the disease was. The only place that seemed to be semi possible was active effects(or something close to that) in the magic menu. No diseases were shown however. I used a cure disease potion and my skill returned to normal. Just kind of frustrating not being told I'm diseased and only realizing I was by accident.

Magic -> Active

That may not have been a disease. A few people have reported similar things with no disease. There could be skill damage that doesn't list an active effect since it's redundant with the skill page.

That's the thing, it only showed my claw attack bonus, and my water breathing ability from a necklace I was wearing.

Redundant? Maybe, but seeing as I cure it with a "cure disease potion" shouldn't it tell me what is causing it. I guessed basically. If it's not a disease why is the solution a cure disease? Also there was no pop up I saw saying "archery lowered by 5" and I only knew I was sick due to beig curious of some perks to pick.