Why do i always sleep around 12 hrs or more and wake up feeling like i've had no sleep at all?

Nonrestorative sleep: You likely have a sleep disorder. Your sleep cycle is being disturbed by something - may be external noise, medications, alcohol, stimulants, gerd, obstructive or even central sleep apnea, circadian rhythm disorder, periodic leg movement, etc. Should see your doc.

Sleep Apnea?: The most common cause of feeling tired and like you have not had any sleep is sleep apnea consult your doctor and you may need sleep studies.