Two weeks after a difficult molar extraction I still have a constant jaw pain. Is not a crucial pain but enough to feel it all day! Is it normal?

Difficult molar extr. I would suggest going back to your dentist and having him take an x-ray to evaluate. There can be a root tip remaining or bone fragment. Or its just taking more time to heal. Do you smoke? That can hinder healing and make it worse.
Not typically. Everyone has a different pain threshold and without being able to examine you or know more details about the extraction, it is hard to make a accurate assessment. However, this is certainly not typical. Some soreness may still be within normal limits, but not if you are in constant pain all day long, every day. You should have the dentist who removed your tooth see you for an evaluation.