Apparently Luvox can cause drowsiness in some people. At least, according to this thread:
http://forums.psychcentral.com/psych...x-fatigue.html

I drank coffee until I had a particularly bad reaction in my early 20s. Over the years I tried to reintroduce it a couple of times, always with disastrous gastrointestinal results. I'm late 30s now, so it was a long while I "got by" on black/green tea + herbals. And for months now, just the herbals. :/

Anyway it's interesting you mention being hypothyroid. I have been on hypothyroid meds off and on since my early twenties as well. Have you had your iron levels checked as well? Currently I'm supplementing to try to improve on a low ferritin count. I have read online that those with low thyroid function can often be low in iron. Elsewhere I also read that iron is required to produce thyroid hormones! (I wonder if hypothyroidism can cause caffeine intolerance in some people?)