Hi Kats,
I'm on Wellbutrin (have been for a number of years) but I remember it feeling like that in the beginning. I really started to feel almost too good in the beginning. But it settled out after a few weeks and now it just helps to keep me level and from sinking too low.
OW was right also, different people can react quite differently. But 3.5 weeks doesnt' sound too early to me for you to feel a difference.
Although it may be that a "normal" level of happiness may feel really intense if its been a long time.
AG