Look at all the divorced celebrities who successfully co-parent (too many to name). There's nothing wrong with you for falling out of love with your girlfriend, and beating yourself up about it doesn't accomplish anything. Life happens.

From everything you've written, you appear to be very grounded (more grounded than a lot of parents who are together, for that matter).

Just remember to be as transparent with your girlfriend about your intentions throughout her pregnancy and after the birth of your child, so that any resentment she may feel (naturally as one does when a relationship ends), is countered by the fact that you were honest with her throughout this entire relationship from start to finish; and that you will remain in her life, in a platonic role, as the father of her child, as a co-parent, and as a friend. That's more than most partners do for their exes, so you are already on good standing as far as I can see.

When navigating relationships, honest/vulnerable communication is necessary to manage expectations and create healthy boundaries with each other.