I got diagnosed with Cubital Tunnel last week. It's like carpal tunnel but on the other side of your arm. I got some Prednisone to take orally as well as anti-inflammatories, and they definitely help short term, but my doc definitely referred me to a specialist so I could get an EMG study done. Haven't gone yet but it gives me some peace of mind knowing I'll hopefully learn exactly what's wrong soon.
I just ordered a gruvgear duo strap because along with the cubital, I've been having nerve/muscle pain on my left shoulder. I'm thinking the cubital is mostly caused by computer work because I find myself leaning on my left elbow constantly during my day job without realizing it. But I think the bass plays a role - a lot of the shoulder stuff happened after one concert where I used my 12lb bass standing for a few hours.
It's definitely no joke, and I'm gonna try to take posture and ergonomics serious going forward. Lighter basses, silly looking straps, whatever it takes.