Meg, oftentimes when you're in the Piecing stage, "bad = good," mood-wise. It's a withdrawal from those giddy highs of waywardness (chemical highs that actually show up on CAT scans!), into the brutal reality of the tough slog that is marital reconciliation. It's normal, and I'd frankly be more worried if he were suddenly giddy again for no apparent reason, as it may mean contact with OW somewhere.
Yes, you have to keep an eye on it, and call him if he's downright RUDE to you and lovingly assert your boundaries. And hopefully his "rubber band" will snap back towards you soon. But surliness is not in and of itself a warning sign -- it's often just the opposite.
Have you asked him what he's feeling? Will he talk to you about it?
