I have all the guards in the Riften city and hold attacking me, they dont accept my yield and Im not sure how to calm them down.. what do I do? Im playing a good character but had to kill some idiot NPC who I accidentally hit and started to attack me.

I haven't run into it Skyrim, but in Oblivion sheathing was not enough, you also needed to hold down the Block button.

Cant be the only one whos had this problem!!

Someone posted something very similar to this earlier- do you have vampirism? You will be attacked on sight until you are cured.

I don't know but,did you done the empire missions on the civil war?That should explain...or it's just a bug from patch 1.3.