It’s not controlling to be exclusive with someone. That is what ultimately leads to marriage…rarely will a man and woman be engaged, and still dating others. Maybe the girls you date are immature…because if you can’t just be up front, and have to feel worried to ask questions, I dunno…something seems off about that.
At the risk of sounding rude and intrusive, the whole non-exclusive thing is off. The arguments raised on favour of it relate better to the
polyamorous movement (with “multiple consenting partners” at the helm) than to what marriage is to be like. If you look at the
“Values within polyamory” entry at wiki, which is an obvious ethical advertisement, the values they define and putatively place in their relationship model are: “loyalty and fidelity” (i.e. to all partners properly inducted), “trust, honesty, dignity and respect” (i.e. by everyone’s being free to make decisions on new partners and by disclosing the information to other partners), “communication and negotiation” (gotta handle all the geometry), “non-possessiveness” (gotta find a major ideological point to justify the thing). This looks very similar to what arguments people raise in favour of non-exclusive dating. Not being possessive, fully disclosing all the information, respecting everyone involved (as a counter to the charge that the conduct is inherently disrespectful), negotiating and compromising and so on.
Obviously, all of the above values, properly defined, are crucial to marital harmony, but the way they are defined
there, they’re not the same values we want in a marriage.
People will raise the historical argument that women used to have more than one suitor, put as the name suggests, a suitor is someone who petitions for something. Those men competed for the woman’s affections instead of a polyamorous romantic relationship being established (which is not to say I have any great appreciation of that form of competition).