I had a similar experience with the two women that were my first poly relationship. My lifemate Jez and I adopted some rules about who and what we were looking for specifically, and it has helped us avoid disaster on several occasions. its good to be clear with precisely what it is you want before you enter into any kind of poly relationship, and not tolerate any deviance from it.
IE, I am jealous of other guys, and very territorial ((stupid triple y chromosome >.<)) but I am entirely indifferent of her relationships with other women. so "no other men" became one of our guidelines. neither of us is interested in "flings" so we do not do that either.
etc, etc, ad infinitum. I hope your experience will not ruin your potential poly lifestyle.