What Causes Sleeplessness Along With Dizzy Spells And Headaches?

I used to drink 2 or more cups of coffee everyday for the last 10 years. Recently I noticed that I was not able to sleep properly at night and feeling very dizzy to the extent I have to stop working. I started on immovable 5 mg nightly. I can sleep about 5 hours. I stopped drinking coffee and tea for a while now. But today I had half a cup of tea and I started feeling very dizzy and also had a headache.