I have a script for Ativan - I rarely use it any more, but have it on hand. It's my med of choice for anxiety on a short-term basis. I've been managing my anxiety med-free for well over a decade now.
Definitely don't take it for a sleep aid - ask your doc about non-addictive over-the-counter aids such as Valerian, Benadryl, or other sleep aids. Make sure you're staying away from tv and the computer, have your room a little cool, no eating/drinking before bed, things like that.
The body jerking? Google (it's okay this time LOL) myoclonic jerks ... could be what's going on. I've had them on various meds - completely harmless.
And yes, your body changes over the years (hormones, etc.) and reactions to meds can change as well. I've had that happen ALOT.