Hi, welcome to the world of non monogamy.
What you are describing seems like casual threesome sex and not polyamory. It can be fun, or it can have awkward moments like you described, and an infinite number of other mishaps.
Group sex can be more fun in fantasy than reality. I personally don't enjoy it all that much because I always seem to try and stage manage so everyone's needs get met. I've done it a bunch, 3somes and a 4some, and unless you're all great at communicating, people can definitely feel left out.
My gf and bf like it tho, so sometimes it happens and I try and make the best of it and not overthink it later. There's always a next time to get that balance just right. I think some people manage it better than others.
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, 34), miss pixi's Dom for 3 years