Dotsie the up and down feeling is normal. I have two sons, and they sort of broke the bonds between us in puberty. I guess that was nature's way of helping me let go; it's simply easier to let go of monster teenagers. (Now they are 30 and 28 and we have, thank God, loving relationships).
If you have a good close relationship with your daughter, I can imagine how hard it must be for you. Sounds like you've been spared from the monster teenage phase, and that is something to be super thankful for. You'll see, Dotsie, when the children leave the house, you will have more time for YOU. You aren't loosing anybody; (they're just a little bit further away) and you're finding yourself again.