Kind of at a crossroads with Scorpio boyfriend...I'm starting to lose interest?

It SOUNDS like he is reconsidering getting back with his ex. (To me.) You are doing the correct thing in not trying to coddle and just giving him space. If your feelings for him are starting to wane that is a huge red flag. (It has only been four months!) I would cut your losses early before you invest too much more time/emotion and move on. Good luck to you!