Well, a low dose of Elavil won't alter your mood, so it won't have an effect on your level of anxiety. 10 - 40mg seems to be the average that people take in order to manage pain and IBS symptoms. You do need to take it everyday for it to be effective.
My doctors have told me that I'd need to take four times as much for it to help w/ anxiety or depression; and at that high of a dose, side effects can include weight gain and fatigue. There are newer, better meds out there for anxiety and depression.
If you're looking for an anti-anxiety med, you might want to try Buspar (which is good for generalized anxiety), but you have to take it regularly. Or you can try a benzodiazepene, like Ativan, which you can use as needed, for those time you're really anxious or for panic attacks.