Here's what rhymes with sleeplessness.

Consider these alternatives

irritability / ability palpitations / relations disorientation / operation constipation / education drowsiness / lousiness fatigue / seek anxiety / variety hallucinations / relations rashes / massive moodiness / broodiness immobility / stability agoraphobia / phobia posttraumatic / dramatic premenstrual / fuel nosebleeds / needs claustrophobia / phobia phobias / copious spasticity / activity overeating / meeting phobia / myopia indigestion / question