Head rush after exercising

Nessie • 💐

I’m 32 weeks pregnant & I’ve been diagnosed with sciatic nerve damage. My physical therapist gave me 6 light “exercises” to do everyday. I have to lay flat on my back to do them so I lay in my floor. They take about 5-10 minutes (at the most) to do & they ain’t strenuous, but they definitely hurt since I’m working a nerve & muscles that need to be stretched. After I’m done I have my fiancé help me up (so it’s easy as possible on me). After I sit up I’ve noticed I get this huge headache right at my forehead that almost feels like a head rush? Like I’ve been dangling upside down for 20 minutes. It goes away within a few minutes, but it hurts like a migraine while it’s there. Is this normal? I know I can’t lay on my back for long periods of time & I don’t. I’m on my back at the very most 10 minutes doing my exercises & I was on my back 30 minutes during my last ultrasound. So I don’t really understand why it’s happening only when I mess with my sciatic nerve.