Fainting/dizzy spells.

I'm wondering if anyone else has experienced this or what the issue may be? I've went to multiple doctors, I've been prescribed with $100 pills and many others and nothing helps. Ive been getting dizzy spells since I was 13, I'll fall over, cant talk, my heart races a mile a min. My head gets clouded it feels like I'm on drugs. Ive hit my head, ive almost fallen down stairs, I've even shaken uncontrollably, the dizziness last for about 15 seconds than I have to sit for a few minutes as my body feels weak and my head feels cloudy. It happens when I stand up (common I know due to blood flow) but I can just be sitting or already standing and get dizzy. I makes life so hard, especially since my son has been born. I cant tell you how many times I've gotten dizzy with him in my arms. I'm at a loss for what to do.