I've been told by other people that I have a geographical/regional acent, but I can't hear it.
Are you from a different region than those people? 
Yeah. I'm from Florida in the US, but my grammer, semantics and dialect seem no different to me than those of my friends elsewhere.
Have you tired recording yourself then listening to it?
I hate the sound of my voice when recorded. But its really difficult to measure or predict how my accent has formulated.
Without hearing your voice or knowing what region yours is being compared to, I don't know how to help you.  
Maybe you could do some lip-reading. I wonder if you can dicern an accent from interpreting the movements of the lips, face and tongue.
I don't think that's possible. I think it's all auditory and even if it weren't, there's no way for me to ready your lips here.
I might have to learn how to read lips. I suffer from some Hearing loss. It's only a partial inability to hear in my case, but it seems to be getting worse.
IF you suffer from hearing loss, then that's the most likely reason why you can't hear a difference between your accent and others around you.