I have two icons under my stamina bar. One is a purple gem or something and the other is a humanity sign, I think.

I haven't found any information on these on any wikis, does anyone know what they are?

They're usually an indicator of what rings you have equipped. Special weapons, like the Drake Sword, also cause some effects.

What rings do you have on?

@Tw1sted: Status effects? You know, like buffs from WoW?

the humanity one is the evil eye ring and the purple diamond is the blue tearstone ring when it's activated i think?

Just check the text descriptions of your equipped items, you will discover some of them give persistent bonuses. Most of the time it's your rings, but other armor or weapons can also give extra stuff.