Hi, my char has a 82 skill level i one handed swords, but now, since today, he has 20 in red..but, I already checked if he had a disease, but he has none, can you help me figure this out..and btw, I play on xbox.

just go pray at a temple or so or rest in a bed

just a visual glitch. level your one-handed skill up again using normal means and it should clear itself up.

Try to go to a shrine and drink a cure disease potion anyway.

When you check for diseases there may be something else in red. Red usually means a disease or curse.