There are a few possible causes here. It could certainly be fatigue and stress that is driving this feeling, but I think since it has been going on for a few weeks that it is worth seeing your primary care doctor
to make sure there is no more serious problem.
Many times when people are stressed, they tend to drink more coffee, smoke more, etc. Tobacco and caffeine are both stimulants and, if they are taken in high doses, they can lead to persistent feelings of jitteriness. I would first take a look at your diet and lifestyle to make sure you are not taking in large quantities of these.
Next, it is possible to have an over active thyroid gland, called hyperthyroidism. This is one of the more common causes of feeling jittery. Other symptoms might include racing heart, sweating, weight loss
, and difficulty sleeping. Your primary care doctor will be able to examine you and perform some simple blood tests to make sure this is not your thyroid gland acting up.
Finally, you may have an anxiety
disorder, which can also cause these feelings. Once again, your primary care doctor would be the first person you should talk to about this possibility.