I congratulate you for giving your sons the best start in life by breastfeeding them!
Breastfeeding suppresses, to some extent, the normal menstrual cycle. It's mother nature's method of spacing out babies so that the one you have gets fed during his or her infancy before the next one is conceived, births, and needs the milk. Mind you, it's not fool proof, you can hear a 100 stories of how it didn't work. In our modern world we tend to forget about what our bodies did to survive, genetics, and the urge to reproduce. Mothers, until very recent and modern times, breastfed their babies until the child could eat what the rest of the family ate. Think about it...we have formula and baby food, 1000's of years ago women regularly breastfed until toddlerhood.
Your body is returning back to the reproducing mode because you are no longer needing to produce milk for an infant. Nightsweats and hot flashes are chemical reactions when your body is searching for hormones. Your brain sends a signal throughout your body looking for female hormones, such as estrogen, when it finds or does not find it, a reaction takes place and you may flush, have funny feelings and or sweat. It's natural and nothing to worry about even if it is fairly uncomfortable.
Hope you are feeling more comfortable soon!