Mindful have you checked your blood pressure? A drop usually makes me feel faint. Sounds like your lungs might be getting squashed too like mine. You are probably yawning to pull more oxygen in. I am doing the same. I have started deep breathing and keeping my windows open. That has really helped.
Jellybaby doggy doesnt work for me either. To much weight hanging off my front now. Me on top usually works since i can control it. And spooning. The choices are fairly limited now. 
My kid cant seem to decide whther to be head down or up. He turned a few days ago. Came up with his head on the left. Now he is trying to complete the circle and go back down again from the right. Feels like he might burst out of me any minute. He is big enough to make me jump with his big movements now.
Hope you feel better soon Spock. I have taken to asking people if they are ill before they meet me after getting sick twice because of people who didnt give it any thought. So annoying that people dont think about it at all. 