"I lie awake at night and I can feel my heart beating irregularly."
If you are aware of your heart when you are quiet this is normal. If you cannot tap out a regular rhythm at all and the heart beat is skipping all over with no regularity, have this evaluated. An extra beat or so every minute or two is normal if the underlying rhythm is regular.

"What is a panic attack?"
These are described as very intense periods of irrational fear. There are four criteria which are met and an experienced physician or nurse practitioner will be able to assess these for you. Some of the hallmarks of panic disorder is that there may be a trigger such as a trip to the store or movie theater which precipitate the panic attack. People who experience these typically describe a feeling of 'impending doom' and will often state that "I felt as though I was going to die".

"Everything is going fine, so why am I anxious?"
Anxiety can be due to changes in your neurohormonal environment which have little to do with your current living and working situation. This goes for depression, obsessive compulsive disorder and many other emotional conditions. Neurotransmitters are the chemical substances in the brain which help control emotions. One common substance associated with mood and anxiety is serotonin.

"Can I get anxiety from taking too many illegal drugs?"
Substance induced anxiety disorder is well described and can be a long term problem resulting from illicit drug ingestion. Cocaine, phencyclidine, amphetamine, methamphetamine and over the counter stimulants such as phenylpropanolamine, ephedrine, phenylephrine and pseudoephedrine can also cause anxiety and irritability.

"I get jittery when I have more than 2 cups of coffee."
Caffeine is a well known stimulant and can even be a cause of anxiety. Different people react differently to levels of caffeine so watch your intake or consider switching to decaffeinated coffee and soda.