It’s most certainly cheating. I’d have zero interest in staying with someone who does that.

Not sure why are you planning a baby if you aren’t fully committed to her?

Now why are you doing it is a complex question. Perhaps you might want to explore it with a therapist? Could also be that you are young and aren’t ready to commit. Nothing wrong with exploring your options. Talking to girls and be causal, as long as you are open about it.

I just don’t think you need to be with someone who is commitment oriented while you clearly are not yet in that place in life. I’d also wait on having babies