I'm Experiencing Extreme Dizziness Especially When I Lay Down (the

I'm experiencing extreme dizziness especially when I lay down (the room spins badly), bend over or lean from side to side. I also have a slight dull head ache and feel generally unwell. The temperatures are very hot where I am but I have been drinking allot of water and staying out of the sun. Thought it might be heat exhaustion but don't think this is the case. The same symptoms hit me 2 weeks ago and lasted several days then went away. They came back this morning and have lasted all day.