Extreme pain standing or when laying down

Hi, I started getting migraines when I was 9, the usual visual disturbance, sensitivity to light, pain in head. Then 16 years ago I was diagnosed with "cough headaches", another form of migraine. In the last 6 months though I have had new symptoms. It started off by waking every night around 3am with a blinding migraine pain and feeling the need to "drain" my head! Upon sitting up, I would literally feel a draining sensation from my head and the pain would reduce, but not go completely for a while. That has now been replaced with being unable to lay down without 3 or 4 pillows, because if I do I get severe pain in my head. The same applies if I turn over from one side to another in the night. Again it's a feeling of excess fluid in my head! In the last week I have started getting a searing pain when standing from sitting, feeling dizzy and nearly passing out. I have to sit straight back down for it to stop. It doesn't happen every time I stand up, probably 40% of the time, and more likely when I've been sat down for a longer period. Can anyone give me any advice please? I really have had enough!