Just for perspective, when my bf comes over (about once a week, we don't all live together) and we have lots of wild monkey sex, when we are done in the evening, I check in with my gf and give her sex if she feels like she wants some. I never mind sex with 2 people one after the other!
We live in a small house, so she can hear my bf and me going at it, and I don't think it's fair to her to let her hear that, maybe get turned on, and be left hanging and unfulfilled. Even if she's doesn't want sex, I let the bf go to bed and hang out with her cuddling and watching TV or talking for an hour or more just to reconnect. Then I go to bed with the bf. He and I get up earlier than her and so we have a morning session too, while the gf sleeps. Mmmm... Everyone seems satisfied with this arrangement.
I hope you can learn to be more confident your needs matter as much as your bf's and gf's needs, and learn to ask for what you want and need. And get it!
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
Mags (poly, F, 61) loving miss pixi (poly, F, 39) since January 2009, living together since 2013
"Master," (mono, 36), miss pixi's Dom for 3 years