we've been togather for over a year now and we've had sex quiet a bit... but he grunted a few days ago..
is that normal?..
Making noises during sex is normally a good sign that they are enjoying it. If he never did before, he might just be getting into it more or his body reacted stronger than usual because his orgasm was exceptionally good.
Another thing, sometime our behaviors change suddenly for no reason you can think of, it just happens. Sometimes through subconscious mimicry: your friend's saying becomes yours; or that saying everyone else uses but you can't stand, then you suddenly realize you are saying it too? Other times there just isn't anything you can trace the change to.
A change of behavior does not have to mean anything bad. If it causes no harm and the behavior change is not so dramatic as to be alarming (brain injury), I really wouldn't worry about it. If it worries you ask him about it.