SPOILERS
You can only get an ending with multiple girls if Stabby Mike assisted you at the finale. The fact that you had to pick between Lauren, Judie, Iris, and Aiko means that you lost Carla's, Rebecca's, and Jasmine's path at some point.
You can now either grab the walkthrough (which you can find among the regular game download options) and try to backtrack and piece things together; or you start over, maybe now, maybe in a year from now, to get the ending with all the girls. If want to do it this way, I made a guidance mod that can assist you along the way.