Hi nouryia, welcome to the board.
Like NYCindie here, I think your arrangement sounds pretty wonderful, especially because your bf makes time to see you twice a week, despite 2 other live-in partners and you both having kids.
I hear you wish you could tell him things whenever you feel like it.
But that's why god gave us internet IMs and PMs and texting!
One social get together and one evening for intimacy sounds good to me... I know when my kids were younger and still living at home, this would have seemed like an unattainable luxury to me.
However, I think your main problem is your fear of fully communicating your desires for even more contact. Even if it's impossible to negotiate more time, I'd encourage you to express your longing. One thing we say in poly is it's all about full disclosure of feelings. Open and honest communication is mandatory. Don't expect people to read your mind.
Maybe you'll be able to arrange an occasional overnight and more online and text communication, maybe not. Either way, you'll probably feel better to let your bf know how you are feeling. Just use "I statements"-- "I wish," "I need," "I feel..." (envious, jealous, lonely, imbalanced, unfulfilled, or whatever it is).
And yes, I do think you're stuck in a mono mindset. Commitment in poly often does NOT lead to shared homes and finances and kids together, happily ever after with a mini van and a white picket fence. Poly brings us other good things: shared interests and activities your other partner(s) don't share with you, good talks, laughs, and lots of yummy sex. Also there is the potential for much personal growth when one gets opinions and views from more than one lover... it keeps us challenged and taking risks.
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