Dose peppermint oil pills help conitsaption?

Uncertain. Peppermint Oil is reported to help with diarrhea & irritable bowel syndrome. Although I am not aware of research on this matter. REF: http://www.webmd.com/a-to-z-guides/peppermint-oil-uses-benefits-effects#1.
It helps IBS. It decreases spasm and pain. If that is the cause of the constipation it could help. Eating more fresh vegetables like spinach or other dark greens , and laxative fruits like prunes, avoiding processed dehydrated salty foods, avoiding dehydration, and getting a good night sleep, moving through the day, and lowering stress will help as well.