41 isn't out of the norm to begin to experience Peri-menopause... I am 48 and in my early 40s the subtle signs of it were fast approaching... one of which are moods swings... low libido (thanks drop in Estrogen) and a myriad of other things....such as the shortening of one's cycle and or constant changes. you can definitely help matters out via good nutrition and exercise.. but it may help your peace of mind to get your hormones checked.. see if you are in fact in the stages of PM...Then I would try and manage it from there..
I found the medical establishment to be of little use when it came to my cycle.. Therefore, I took matters into my own hands and began reading up on it.... I was determined to figure out what was going on with my body.... I read books like, Screaming to be heard, a book by Dr. Elizabeth Vliet.. It is packed full of info with regard to women and their hormones.. she has other books out there as well....
Good luck in whatever approach you take