Cold sores are a type of herpes just like chicken pox and shingles is. No need to feel "dirty", its an illness caused by other things (I have a friend with mouth and throat full of ulcers like that from his Crohns disease). It's necessary to take a swab and figure out what is causing yours so the correct medicine can be given to help it (my friend has to have steroids, for example, to cure his).

http://www.mayoclinic.com/health/cold-sore/DS00358