Congratulations on what seems to be a great relationship. Not many people truly get to the comfortable and happy stage where you don't have to play games or worry so much anymore.
But now what happens is that you're worried about losing that feelings. This is a fair concern, however, you can also think yourself right out of a good thing. Sometimes you have to let the relationship exist and breathe all on its own without trying to control the outcome. Hell, the truth is, you can't. A relationship requires two people to allow somebody else control over their lives and feelings. Since you no longer exhibit those insecurities that usually create barricades towards that security, you should be okay and just let it go now. Enjoy it. Don't worry about it.
And ultimately, keep the lines of communication open and address issues if they need to be addressed. But it sounds like maybe you two have got it working.
So smile. Breathe. And live, laugh, and love.