I've gone through more or less the entire spectrum of feelings when it comes to the intrusive thoughts I experience as a result of OCD. Occasionally I will indeed feel dirty; like when I develop an irrational (but always totally private) obsession with a woman, or some sort of sexual fetish that I can't let go of. But mostly my emotions are more negative, being predominantly along the lines of guilt and shame when I'm having racing thoughts regarding violence or what have you. Those are the ones I struggle with most, since I can handle being a closet perve, but not a closet serial killer.
EDIT: not sure if the OP meant dirty-minded or actually physically grubby - I went with the former, sue me. :

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