The simple answer is that the Prozac will take about 2 weeks at minimum to show some benefit, and most people experience more significant symptom reduction in 4-6 weeks with 8 weeks being full effect. It is, rather a slow process.
Prozac works by increasing the availability of serotonin which reduces anxiety and worry (as well as depression). Ativan is a benzodiazapine, which increases a chemical called GABA, which tells your nervous system to stop sending messages, particularly fear based messages. The Ativan is very dosage dependent, very fast acting, and if you are not getting any relief you may wish to talk about dosage with your doctor as usually this medication is highly effective. You may just not be taking enough.
I would recommend a revisit to your prescribing doctor as at least one of these should be giving you relief. And, in all likelihood, the dosage is simply not adjusted to your metabolism. Steven
As you are already at the upper limits of the usual dosage they most likely, instead of increasing the dose further, will change to another chemically similar medication. These include Valium, Xanax and others. There are many, many others in this class of medication, and I know you are in distress, but please try not be too discouraged.
Even with all the neuroscience at our disposal, dosing and choosing the right medication is still very hit or miss. But, in retrospect, I doubt they will increase the dosage. They may increase the initial dosage and taper it later in the day, but more typically at this point they will try another medication as you seem resistant to this particular brand. Steven