Keep in mind that obsessing is your mind's (incorrect) belief that you can control a situation. You can't.
Think about who your SO would find attractive...is it someone who would yell over text message "WHY WON'T YOU TALK TO ME"? Doubtful.
I wouldn't worry about his ex although maybe she had some insights that were helpful. You are speculating about their relationship...another dynamic you can't control.
Do things for yourself, focus on you...to quote a common phrase on here..."be someone only a fool would leave".
I know it's hard...I struggle with it every day and I obsess. But, I really try not to show that to my H. You will slip up, but you need to control yourself over things like text messages.
M 44, H 46 D11, D9, D5 Married 12 years PA confirmed 9/2011 I filed 3/2012 H moved out 7/2012