It's great that you and your ex no longer hate each other's guts, but you broke up for a reason. Even if you have your ducks in a row now, the two of you still did not have a strong enough relationship then to weather the storm.
If you are in love with your girlfriend, then that is where you need to be. My advice would be not to marry until you have sowed ALL your wild oats and are 100% ready to settle down. You don't want to end up like some of the homewrecking, child abandoning bastards that turn up here every now and then.
My personal opinion (and I say it again: OPINION) is that now that your ex is no longer taking the rank of evil hellbitch that doesn't mean she shouldn't still be a blur in the background. Put her back in the past where she belongs and move happily towards your future full of bunnies and kittens and rainbows and nice shit like that.
There are very few personal problems that cannot be solved with a suitable application of high explosives.