What would cause a P.T Cruiser to lose mph and not go anywhere

Sounds like transmission problems to me. Check your transmission fluid. If it is very low, you need to find out why. Probably a broken cooler line, (going from the transmission to the radiator) bad transmission output seal,(where the axles come out of the transmission) or front pump seal. (leaking between the engine block and the transmission housing) If it smells bad (like burned oil) and is dark brown, your transmission is burned up.

Sounds like you lost your transmission -check the fluid level?
Check the color of the fluid --does it look dark and smells burnt? That's bad news.