Thank you so much to all of you who put him in your prayers.
We saw a specialist today. Joints are all okay, bloodwork looks good. No obvious signs for the discomfort/pain he is in. What did come up was an irregular heartbeat and signs of atrial fibrillation. However, he's in pain and atrial fibrillation does not explain that. For those that don't know, atrial fibrillation typically just makes you feel lightheaded, dizzy and just "off" in general. He responds well to pain medication so while the atrial fibrillation might be related, there's something else going on.
Next steps are going to be an EKG and an echocardiogram and most importantly (in my opinion) an X-Ray. He's very large (175lbs) so we'll be taking him to a local university as soon as they have a slot open. In the interim, it's just going to be keeping him as comfortable as possible with pain medication and love.
I humbly ask for you to keep him in your prayers. I love my boy and I'm very worried this could be something serious. He's too damn young (4 years) for me to lose him.
Perhaps try a chiropractor and/or an acupuncturist who works on animals. Holistic/natural medicine/treatment is often better at diagnosing afflictions and healing them than "modern (human and veterinary) medicine".