If I had to guess, I would assume he's getting absolutely murked by wolves in the mountain region (since you say he just beat bonemass). Those wolves are a serious problem, I honestly believe they need some balancing. Once he progresses a little further, they'll become easier, but they swarm you early and often and blocking their fast attacks takes all your stamina then you die every time. I was SO frustrated when I first started the mountain biome, made me want to stop playing for a while. Keep in mind that I found the rest of this game pretty easy, and I have mastered bloodborne/dark souls. The wolves are too OP for folks fresh out of the swamp biome.