Horse loving mama
I would stop the lunging period. Just curious with him being 14 why the lunging? A good lameness vet that knows what to look for would be the best place to take him, all the others are just guessing at what your horses issues could be, at least a vet can pretty much pin point the issue for you, sometime it could be a shoulder problem, deep abscess, deep bruise, tendon, ligament could be anything, Vets have the trained eye and knowledge for this. I know money can be a issue, but when you own animals you have to suck it up and do the right thing for them, being a animal and horse owner this is what we do.