A good run of form for Aidy Boothroyd's side was brought to an end by the U's with the home side opening the scoring through Constable on 15 minutes.
Clive Platt levelled with just under 15 minutes remaining but Boothroyd will have been disappointed to see his side concede the winner to Pittman just a short while later.
Town now lie in 10th place, 2 points behind the play-off places.
Full report to follow on Cobblers Mad.
Source: Cobblers Mad