Advice!

Hey ladies! So I’m 27weeks 3 days pregnant and when I lay flat on my back it feels as if the blood from my head is leaving my brain, as if I’m being held upside down. I do drink lots of water so I’m sure that’s not the case, and when I lay flat on my back I also feel slightly light headed and I feel like oxygen isn’t getting all up in my head and I’ll get a slight pressure on my chest but it isn’t painful, just uncomfortable . 😂 has anyone else experienced this?