
You may also consider things that are driving your asthma at night. For example, GERD can occur more often when you are laying down. Have you been checked for GERD? This is when contents from your stomach spill into your esophogus and irritate your breathing. It can cause heartburn and spasming of your larynx, though sometimes it is "silent" (symptomless). Along with GERD, I would look into the possibility of sleep apnea. This is a sleep disorder where your airway does not open all the way when you sleep. This can cause snoring and lapses in breath that can occur hundreds of times a night.
With that being said, between 2 and 4 is also when most asthmatics wake up. They find that this is when your body's natural anti-inflammation curve is the lowest.
In any case, if you are waking up at night, no matter how common this is, it is not a good thing. You are not controlled and you need to be. Are you on any type of inhaled steroids or long-acting bronchodilator? You do need to talk to your doctor about this!