First off, 50mg is a large dose to start off with and going from 50 to 100mg is a big jump--you could be having higher anxiety from the increase. Second, it's only been a little over 3 weeks, so it's not surprising that you're still jittery and anxious.
I'm almost 6 weeks in on 50mg (12 days of 25mg before that) and haven't seen a huge improvement, but my doctor likes to take things very slow, and wanted me to wait 6 weeks. I'll be going up to 75mg probably tomorrow.
Hope it kicks in soon for you!!