Elin Nordegren -- 'I'm Happy for Tiger' ... But I Can't Forget How He Hurt Me

Elin Nordegren says "the word betrayal isn't strong enough" to describe how she felt when she learned Tiger Woods had been banging around behind her back ... but says she's finally moved on.

Elin opened up to People ... saying she felt "safe" with him during their marriage and that's why it hurt so badly when she found out about the legions of skeezers he was nailing on the side.

"I have moved on, and I am in a good place. Our relationship is centered around our children, and we are doing really good -- we really are. He is a great father.”

TMZ Sports broke the story ... the former couple attended their son's baseball game together recently -- with Tiger's new girlfriend Lindsey Vonn -- and they all seemed to be getting along fine.

"I’m happy for Tiger ... In general, in any kind of step-parent relationship, I’m happy that there’s somebody else loving my children."