me and sleep are not getting along

For some reason I have been having the hardest time sleeping. I have never really had a hard time sleeping, usually I sleep like a champ, unless I'm pregnant of course. But for the last 4 or 5 months I cannot sleep at night! It takes me hours to fall asleep and I wake up like every half hour throughout the night and can't fall back asleep. I just toss and turn all night. It is so frustrating! I'm not particularly stressed or thinking about worrisome things.......I don't drink caffeine (often)....I've tried Tylenol PM but all that does is help me fall asleep fast but then I wake up a few hours later with the same problems......I've tried herbal "cocktails" like Valerian root and passion flower and a bunch of other herbs in there, but they don't do a thing......I exercise almost everyday and that's what doctors tell you to do when you can't sleep. So I'm out of ideas. I feel like I am up all night and when I finally fall asleep for a decent amount of time my kids wake up and I have to get up. I don't know what could cause this to happen all the sudden but I'm about done with it.