It's hard to diagnose something without seeing or feeling it. I would take him to the vet for a checkup. He/she could tell you what they were. They could just be fatty tumors or cysts, but I would take him in because it could be cancer. You never know and it's best to catch it early. Good luck!
Sending good vibes.
i agree a vet check will tell you a lot more then we can. we have a male who has 2 fatty lumps on his under belly, he had tests done and all came back clear, and because it dosnt bother him we are not having them removed unless needed.