...I was afraid of my insecurities and jealousy...
There is a huge difference between thinking about it hypothetically and
KNOWING your boyfriend is off somewhere with another guy's cock up his ass.
Open relationships are harder than monogamous ones, and you shouldn't be in one unless you have the confidence and maturity to deal with the reality of your partner having sex with someone(s) else.
A lot of guys have this idea that it's hedonism 24/7, and it may look like that from a certain perspective, but underneath there has to be a rock solid commitment and understanding you have to maintain if you don't want it to implode on you.
...but I also know that the idea of cheating is essentially non-existent in an open relationship (well, unless it's emotional cheating)...
Cheating is still cheating, any violation of trust is cheating - emotional or not.
Rules.
1. First priority, if he's somewhere else, he comes if I call.
2. Power of veto, for any reason, for no reason.
3. No standing repeat customers without prior consent.
We got into this because he's living 2000 miles away for the near future and neither of us are jealous kids worried about the other guy needing to get off. But it's probably fair to say that I've also known him all of my adult life, we've dated before, broken up before, watched each other date other guys, watched each other go hog wild and just about every permutation thereof, and still ended up together in the end.
I know I can trust him, because no matter what, he's always come back to me. He knows where home is.
I don't know how long you've been together, but if you're just starting, you might want to get to know each other before you take that step.
It's so incredibly common to find guys who start wanting to "open," their relationship because they aren't getting something they need out of it.