It has been around 8 months since I played, so I started a new game after downloading Dawnguard. I am now at lev. 9 and vampires are showing up. Were there vampires in the origanol before Dawnguard, I do not remember. Also can you be infected (like in Oblivion) and turn into a vampire? or is it a choice you make?

There were vampires before DG, but they weren't emphasized and as powerful as DG. You get infected by getting hit with drain life spell, then after 3 days you turn into a vampire.

THe vampire attacks on cities and settlements is added with DG and can be very troublesome as shopkeepers get killed sometimes.

Yes I have unfortunatly found out. I suppose there is some long drawn out way to cure myself? Don't tell me the answer just a yes or a no will do. Unless just eating something or taking a cure desise potion will work. oh yes does Your companion get infected

Becoming a vampire is easy to prevent. So there's no reason to be one unless you want to.