I have chronic insomnia which I believe is from General Anxiety Disorder... Has anyone else used SSRi (such as lexapro) to treat the anxiety disorder (thus, alleviating the insomnia)?

I've tried sleep meds but they all stop working after about 3 days and some don't work at all.

Seroquel 50MG: stops working after 3 days
Ambien: didn't help me sleep at all
Doxylamine: stops working after 2 days
Trazodone: bad side effects

I've just started Lexapro and am hoping it will help my insomnia (although I've heard it can cause insomnia... my insomnia can't really get any worse than it is so might as well see if this helps).