Spider
I do not think you are being honest.
With yourself.
What is it you are searching for that is not in your marriage?
Are you wanting the thrill of a new partner? Are you bored sexually?
Are you wanting an emotional connection that is not there in your marriage?
You see, these are the only things that someone other than your DH could offer.
It does appear that you want to have your cake and eat it.
You want the security of marriage- but the thrill of new relationships and encounters.
Talking openly about this does not validate those feelings.
it does make your DH feel insecure and presumably that he doesn't fulfil you in some way.
If you want non-exclusivity then you have , I think, to take everything that goes with that. That means accepting you might fall for someone who won't commit to you. It means you might have fallow years when no one is available. It definitely means you can't have the safe and comforable backdrop of your marriage while you test the waters.
IMO most people who do not want monogamy are quite self-sufficient and are happy to be alone for much of the time. They are happy to have encounters that are transient. They do not look for love; and they don't offer it.
This is a very different mindset to yours. You appear to be searching for something ( and i think you really must define what that is) which is not on your life now.
If you want variety and all the insecurity that goes with it, then leave your DH because your honesty is just pure selfishness, and a form of torture to him- do you realise that?