What Causes A Black Eye And Loss Of Consciousness?

Had a black eye friday morning when i woke up with no apparent cause. 20 minutes later I fainted. Went to ER, they ran a battery of tests (cat scan, chest x-ray, carotid doppler, echo cardiogram, heart stress test, blood work) all came back normal. Blackened area above my eye is growing, and I almost fainted again this afternoon (lying down stopped it). I feel pretty weak and light headed. Do I head back to the ER?