I sometimes have hallucinations when i close my eyes, usually before sleep. most often this happens when i am sick, or tired. am i a mental case?

No you are NOT: Sleep consists of multiple stages & cycles. A typical sleep cycle starts with transition from wake to stage N1, then stage N2, stage N3 & then REM. Stage 1 is the lightest stage & anyone awaken from it do not perceive that they were actually asleep. You feel hallucinations when you wake up from stage N1. It is normal. But for obese person it could be an early sign of obstructive sleep apnea.