Hi Addy! Welcome to NT!

What you describe about passing out when you stand sounds like what my neighbor lady does. She missed her own dear son's funeral b/c she passed out in the bathroom and it was 2 hours before they could revive her.

Not sure exactly what she is dxd with, but it has to do with her blood pressure dropping, like you described.

I wonder if Melody is on to something that could help you?