My first ball python

[Bogertophis]

This to me is the only really noticeable one- -where I can see the bulge just above his cloaca.

He may be just about to "let it go"- with a little more activity (ie. handling), & assuming adequate hydration (what's his humidity kept at?) plus clean drinking water at all times. In any case, he's not starving.

Have you GENTLY felt that area just above his cloaca where the bulge is & found no hard lumps? If he had a urate "stone" blockage, that's most likely where it would be.