I had a pulled ab muscle strain 3-4 weeks ago and last week I shoveled snow now I am getting pain under my lower rib cage. .. Is it from shoveling?

Yes. Yes shoveling snow can definitely cause strain of the back as well as abdominal muscles .It can be strenuous especially if it the heavy wet type. Usually the pain will resolve in couple of days without any long term problems. If you continue to have problems see you doctor.