I need help?

Am a 42 year old woman in perimenopause.I have been on treadmill faithfully 8 weeks for 45-55 min 6 days a week. Warm up 5 min (2 min @ 2.8mph and 3 min @ 3.2 mph) then do 35 min (16 min@ 4.6 mph jog and rest at 3.6 mph, jog time is not all at once..is 3.5 min X 4 +2 min with walking breaks in between). Do a five min cool down same as warm up;total distance usually 2.93 miles. Can't seem to get my heart rate up beyond 75bpm even during the jog times; yesterday I increased my mph during jog to 5.7 and still didn't get it to target heart rate (115-140) I already limit starchy carbs. I have been measuring target areas, (arm flab, waist, upper hips, lower hips, chest and top of thigh) and in 8 weeks very little improvement in anything; don't have scale, but weight not dropping, either. Nothing moves..Between July 2003-Feb 2006 lost 65 lbs. on Atkins with virtually no exercise, gained 20 back with new man who likes meat and potatoes..now married..Getting hopeless..Please help