I have just started experiencing this myself, but at about 40 hours into the game. I play a Breton stealth/archer character. I have found no explanation or fix for this yet and it is very frustrating. I believe it started after fast-traveling to Whiterun, but I can't be sure. I just noticed I was suddenly staring everyone in the bellybutton. Also, I cannot sprint properly. Instead, I do a short dash and stop, using only a fraction of my stamina. However, everything works normally in third person view, except I hate playing in third person. >:(