Pounding head when standing!

Tasha

So I've been off work for 10days to rest due to Nausea and sever back pain, so I've been resting up and spending a lot of time in bed! Last 3/4 days everytime I stand up I have a pounding headache, but as soon as I get back into bed it subsides... it's still there but not as bad ☹ I'm 10 weeks pregnant, anyone else had this?