Yep, what you're experiencing is perfectly natural. It's got sound biological basis and is not a 'failing' on anyone's part. Nor does it reflect badly on your relationship.
I'd suggest picking up a copy of "Sex at Dawn" and both reading it. Preferably before you take action. It will do much to put what happens in the future (potentially) in proper context. And this goes a long way towards keeping jealousy in check. Will it still rear it's ugly head ? Probably. But when we understand something it's not so scary and dramatic.
Keep us posted.