I sure hope the antidepressant was given AFTER every other medical possibility was ruled out. Were you tested for thyroid function, diabetes, anemia? Have you seen a sleep specialist to rule out sleep disorders? Maybe the antidepressants aren't working because something else is contributing to how you feel.
You might be suffering from hypersomnia. It may present as excessive daytime sleepiness or nocturnal sleep of long duration (as much as 12 h or more) or sleep drunkenness. Patients do not get abnormal amounts of night sleep rather they have problems waking up in the morning and staying awake during the day.
The causes can be genetic, brain damage or medical disorders such as clinical depression, uremia and fibromyalgia. Sometimes hypersomnia may be due to other sleep disorders such as narcolepsy, sleep apnea, and restless leg syndrome. Your symptoms may be linked to depression. Try relaxation exercises, meditation, change life style etc.
You should consult a sleep specialist for a complete medical and psychological workup.
Take care and regards.