"Letterman Jackets" joke

OKay, this chick walks into a pharmacy. There's a guy at the counter.
The chick says, "Doctor! I need your help!"
He says "What do you need?"
She takes off her shirt and she's got this big' O' on her chest. She says, "How do I get rid of this?"
The doctor said, "how'd it happen?"
She goes, "Well, whenever I have sex with my boyfriend, he wears his Oklahoma University jacket!"
The doctor said "Just tell him to take it off."
She said "OK."
And then this other chick walks in with the same problem and goes,"Doctor! Help! I've got a big "F" on my chest!"
He was like,' Holy crap, another girl with the same problem?' and he says, "Just tell him to take it off."
And she said "OK."
And then this third chick walks in with the same problem and says, "Doctor! Help! I've got a big "W" on my chest!"
The doctor was thinking,' What the hell! Same thing again!' He says, "Lemme guess. Your boy friend goes to Wisconsin U and when he has sex with you he wears his jacket."
And she says, "Well, not quite. My girlfriend goes to Michigan."