I do not mean to laugh, but you really are a worrier. Stop it, you're fine. Perhaps this isn't the best thing to tell you but with or without condoms you can get her pregnant. With or without birth control you can do it too. And doubling up on any of it doesn't matter. If one form of protection isn't enough, the others won't be either.<-a sex ed teacher told me that one. In this case it sounds like you are pretty safe. I mean you've never gotten her pregnant. Before and I doubt very highly that the 20-30 seconds you were without a condom you passed much of anything except a little blood. (this is normal as your penis would be filled with the stuff and it excretes tiny amounts anyways.) Most pre-ejaculate is simply lubrication. Yes it does contain a small amout of sperm too but it is so small that the females spermacide would most likely be plenty enough to kill them.
Many couples try countless times to get pregnant. But just can't do it. Others have sex once and boom here come twins. Its totally hit or miss, and nearly completely random. There are suspected ways to increase your chances yes, but if you protected her from the "main stream" then it is unlikely that you impregnated her. Very highly unlikely by the way.
My opinion is that you really do not have much to worry about so just relax. But also remember that if on the extreme off chance you did get her pregnant, a baby is a wonderful gift no matter when it comes and you need to man up and take care of your own.
but like I said, I doubt very highly that you have anything at all to worry about.