07/19/2011 02:23 pm ET | Updated Sep 18, 2011

Elin Nordegren Boyfriend Jamie Dingman: Relationship With Tiger's Ex-Mistress?

Elin Nordegren is PISSED ... after learning Rachel Uchitel told friends she had slept with BF Jamie Dingman. Now Jamie is denying it happened, but others are providing VERY specific details.

Sources tell TMZ ... Elin was blindsided when the TMZ story ran over the weekend ... that Tiger Woods' #1 mistress had slept with Jamie and Elin didn't know about it.

Read more on tmz.com