I saw your post on the vet board and sent you a note, but I just said what these others stated on here as will. If you don't have a good vet, ask others in your area who they like and why. I had one vet harm my dog and later discovered that no one else like that vet either. Note, most vets are good.
I would take him to the vet, sure. Find out what those lumps are. They may be benign (harmless) but it's always good to know. The vet may do a "needle biopsy" on them. Don't worry about that. My dog has had 3 before. Usually no anesthetic is needed, and you can stay with the vet while he does this, and help to hold Bear steady perhaps.
He may be crying when you pick him up because he has some pain in his belly. Or it may be joint pain. Either way, this needs checking out, and maybe some meds to help.
10 for a mixed breed (medium or small-ish?) isn't too old really. So don't let anyone give you the impression he's too old for the best of care! My dog's older than him, and still (so far, thank God) running around like a young 'un.
I do hope Bear is OK, and this is a bad patch, and hopefully with the right diagnosis and treatment, he'll be just fine. Please do let us know, if you can, what happens. Good luck, Bear.
YES, take him to the VET asap he sounds as if he in pain.