For me, the idea of knowing too many details makes me uncomfortable (at least in the early stages). Even now, I have no interest in knowing how many times Dude has sex with Lotus when they are together...I just want to know that they both had a good time and are happy with how their relationship is proceeding. (And the reason I want to know even that much is because I am friends with/involved with her as well, as is MrS - so there are multiple levels of caring involved - I want everyone to be happy/satisfied on many fronts.)
Maybe you need to step back a bit. NOT know when/how many times they have sex. Ask him not to "overshare" - so you are not tempted to compete. Focus on your relationship with him - are you satisfied? Are you getting the attention (physical, emotional, intellectual, etc.) that YOU need? If not, then ask for what you want explicitly (for yourself - not in relation to what she is getting).
Me: poly bi female, in an "open-but-not-looking" Vee-plus with -
MrS: hetero polyflexible male, live-in husband (23+ yrs)
Dude: hetero poly male, live-in boyfriend (4+ yrs) and MrS's best friend
Lotus: poly bi married female, "it's complicated" relationships with Dude/JaneQ/MrS (1+ years)
+ "others" = FBs, FWBs, lover-friends, platonic G/BFs, boytoys, etc.
My poly blogs here:
The Journey of JaneQSmythe
The Notebook of JaneQSmythe