May I seek relief under MA's alimony reform due to the fact that my ex-wife and her boyfriend have been cohabitating for exactly one year?

My ex wife and her fiance have been very public (conversations and Facebook postings) about their engagement, but have no specific wedding date set. They have lived together since July of 2012. I pay alimony, continue to have her covered under my health insurance, pay her auto insurance and dental insurance. My work week was reduced (by my employer) from 40 hours per week to 32 hours per week. My alimony would cease upon her remarriage, however, my ex is reluctant to announce any formal marriage plans despite being engaged. Although our relationship is amicable, I feel I am being taken advantage of, due to their reluctance to discuss their future marriage plans.