Is it an actual bone hematoma? (like, bleeding under the periosteum from a fracture?)

Is it a tendon? Is it the muscle tissue?

Is it just the skin that bled? (subcutaneous could be from the muscle tissue, and just hanging out under the skin layer, or could be from the skin itself)

Does the doc know where the actual source of the bleeding is?

I doubt it's the stitching of the saddle - that would more likely lead to a surface critter than to a critter deep to the skin.

Can you take your entire bike to a pelvic rehab PT and have them check your fit? Take any other saddles you may have lying around, too. Even if the PT doesn't know bike fit, they *will* be able to see how the saddles interact with your body as you pedal.