Week #4 is still very early in treatment with an anti-depressant such as Citalopram. Also, what dose are you on? The reason I ask you this is like all ant-depressants, Citalopram (Celexa) has a minimum therapeutic dose, that being 20 mg. If you are on less than 20 mg, you may not be benefiting much at this time.
I am on Citalopram, have been on it since last November, and it has really helped me. It did take time to work. I saw a decrease in depression and intrusive thoughts at about 3 weeks into treatment on a therapeutic dose. My anxiety didn't really decrease until around week #10. It takes time to repair our brain, so one must learn patience when dealing with anti-depressant therapy. I too have had some "numb" days, and days that I didn't really feel I was all here. These are not unusual, and they shouldn't last.
Even now, I have some off days, but mostly good days, and I am thankful for each one of those.
The very best to you, Will!... Chuck