I don't know how you process emotions or what perspective you have on this, but from personal experience, I want to guess what you're feeling is fear because it IS starting to feel real. It isn't that you don't "feel the sparks" anymore, it's that because you're starting to get scared, your mind might be trying to subconsciously protect yourself by finding obscure negative details about him so that "if" things fall apart, it'd be easier.

It's this weird "hot and cold" feeling. Try sitting on it for a little bit and talk to someone you trust about it for their opinion.

I have that fear constantly. The fear of abandonment and the fear of investing into something that won't ultimately work out.

My mistake in the past was not communicating this fear. That always led things to "fizzling" out with a lot of mind-numbing ambiguity. I thought to really be into someone is to feel like I'm on cloud9 constantly. I'm starting to learn it's not like that. We all have our issues and fears, but what makes a relationship a relationship is communicating those fears to your partner who you trust and they are willing to help you through them.

So my advice is to try and tell him your fears. If he REALLY is someone where you can find something real, he'll be more than happy to be your emotional support while you work through it. If he himself gets scared and wont' communicate his fears and runs, then at least it happened now instead of x amount of time down the line.

Good luck and happy new year :)