Three times a day IS a lot of sex. I thought I was extra horny because I'd like to get it once a day, or maybe twice if both my partners were available and in the mood.
Back when my bf was 20 miles away, we only had one day a week together so we'd have 3-5 sex sessions in 24 hours to tide us over. Then I'd get to have sex with my gf once or twice in the week as well, MAYBE 3 times, if I got really lucky.
Anyway! Enough about me. If I were in your situation, I'd feel a bit concerned about all these dates my partner was going on. Partly because multiple partners open you up to STDs. Even if she's using condoms for intercourse, I doubt she's using them for oral, or dental dams for receiving oral from partners or giving oral to females? She could get herpes or Hep C.
Also, you say you're living together but she's off for days on end with other casual partners? I wouldn't be able to live with that either. That seems excessive. I mean, she can do what she wants, but how do you deal with having a so called gf who is hardly ever available? There is more to a relationship than sex. There's dinners together, activities, housework and home maintenance.... Do you want a live in partner with a bit more commitment than she is willing to provide?
As for your "indifference," I also know what you're feeling. This summer has been very stressful for me (I moved house, got a new job, my gf had some emotional trauma I had to help her with, a guy I attempted to date tried to kill himself), and yet my bf has been dating or trying to date 3 others. (And I partly moved to this area to be closer to him, as was also his frequently stated wish!) I didn't have energy resources to deal with the emotions I had around that... so in some ways I shut down towards him for a while, felt less bonded. I felt insecure that so much of his emotional energies were going towards these 3 new people. I felt like just one more pussy to him. After all, he has me, a wife, and also a connection of some intensity with my gf already!
Some people are just "too poly" I think! I've decided to stop dating anyone new just so I can deal with my emotions around all his new people!
Love withers under constraint; its very essence is liberty. It is compatible neither with envy, jealousy or fear. It is there most pure, perfect and unlimited when its votaries live in confidence, equality and unreserve. -- Shelley
me: Mags, 59, living with:
miss pixi, 37