Richard Simmons’ housekeeper of 35-years has her own theories about the fitness guru’s cause of death. Teresa Reveles shared what she witnessed in his final days and why she theorized he died of a heart attack, RadarOnline.com can reveal. Reveles began working for Simmons in 1986 and proceeded to live with him for the next 35 years. During her time working for Simmons — who died on July 13, one day after his 76th birthday — she gained intimate insight into the fitness icon’s personal life. In her first ever interview, Reveles confessed: “I can’t stop crying. I still can’t believe what happened…