Your relationship is what you make it my dear. The reason why both of you have not walked away is not just your son but the fact that you love each other. Do not parenthood alter your feelings for each other or make you stop doing the things you used to do for each other. Go back to those things that made you fall in love with each other in the 1st place, rekindle that love, spend time together, go out for a movie..... Love just doesnt fade away.
I know you will make it work