What Causes Insomnia, Nightmares And Hot Flashes During Menopause?

I am a 48 y/o female going thru menopause for over one year. I haven't had a period since August and pelvic ultrasound shows thin uterine lining. I have been experiencing the usual symptoms such as hot flashes and mood swings, but over the past week I have been experiencing severe symptoms such as insomnia, nightmares when I finally do sleep, extreme hot flashes, and worst of all, uncontrollable crying and bouts of anger. What can I do? I can barefly function at work, every little thing completely sets me off or incapacitates me!