I don't think so. He sounds like a perfectly healthy chubby bub. My kids all had pretty huge growth spurts early on. They just grew and grew until about 12 months and then really slowed down for a long time.
My friend just recently had a baby (he's 9 weeks) and sounds to be a similar size. He was smaller born, but has grown a similar amount. He's also fully demand breast fed, and pretty frequently.