I've had some of the same symptoms and spent a lot of money over the last year trying to get a definite diagnosis, with no luck. The first thing I'll say is, don't believe anyone who tells you that an ear problem will heal in a couple of weeks. Damage to the middle and inner ear can take months to heal, and may never fully heal. Worse, because it is behind the eardrum, it's impossible to see and a doctor who isn't familiar with diving barotrauma is likely to give you the "all clear" way too soon. If you don't believe me, read up on some of the things that can go wrong:
http://american-hearing.org/disorders/perilymph-fistula/
I have constant problems with vertigo and tinnitus when diving, but there doesn't appear to be a definite cause. I'll throw my case study out there in case it helps anyone.
I'm male, age 37, and have been diving for 24 years. I got kicked in the head while playing underwater hockey last year, and didn't think anything of it until I got out of the pool at the end of the night and discovered that I had such bad vertigo that I could barely stand up. I also had fairly bad tinnitus, but I have always had problems with exercise induced tinnitus, so I wasn't too concerned. The next morning, the vertigo was worse, and I had a pronounced hearing loss in my left ear as well as the tinnitus. I went to my PCP, who said the eardrum looked slightly inflamed, and had some fluid behind it, but there was no perforation. They suggested I take pseudoephedrine for a few days, and come back if the symptoms didn't clear up. Within three days, everything was back to normal.
I took two weeks off from underwater hockey, and then resumed playing. I made it through several sessions with no problems, then about a month after the initial incident, I got hit with vertigo and tinnitus again. It was not quite as bad, and again it cleared up within 3 days. I took two months off before trying again, with the same results. At this point I was pretty sure I had some kind of inner ear problem, and scheduled an appointment with an ENT. After describing the problem to the ENT, he referred me for vestibular testing.
The vestibular testing came back as severely abnormal. In discussing the problem with the specialist, I mentioned that the Valsalva had caused vertigo ever since I began diving, and I just assumed this was normal. To clarify, I'm not talking about alternobarovertigo (which is normal); in my case, sustained pressure against the inner ear for more than a few seconds causes severe vertigo which stops as soon as the pressure is relieved. This combined with the hyperacuity in my left ear (which I have always had), made them suspect some kind of serious structural problem in my middle/inner ear.
They ran me through an audiogram (perfect hearing), CT (normal), MRI (normal), and VEMP (normal). The final conclusion was that I have something wrong with my left ear, and my vestibular system is seriously screwy (I just never noticed), but they couldn't find a cause. The official recommendation was to stop diving completely, but even the specialist admitted that since they didn't know what was wrong and the few major episodes didn't seem to have caused any permanent changes it was really my call. Given that I've had some of these symptoms my entire life, I decided to give things six months to heal, then try again.
Since I started diving again six months ago, I've only had one vertigo attack that was serious enough to give me trouble, and it settled down within a few hours. I've given up on underwater hockey, and am extremely careful with ears.
On an unrelated note, I have also started using mineral oil in my ears before every dive. It feels kind of gross, but it keeps the tissues in your ear from getting waterlogged, which in turn reduces the risk of getting an ear infection.
