I am 45yrs, and have always have regular periods, clockwork.?

Sounds like you may be going through the change of life. It effects people differently....Mood swings, depression, hot flashes, night sweats, lack of concentration, diet can change, fatigue, nervous, lack of patience, poor sleeping habits, headaches. The thing to do is go to the Dr. to be sure, they can do a blood draw to see if you are going through menopause. There are meds they can put you on and they will help.