laying on your left side is the best way to keep your blood flowing for the baby... The pain is coming from you possibly blocking a major artery that supplies for your baby

Varicose veins are in your legs usually and aren't going to cause pain in your stomach. These veins are very visible. It's probably not that. Usually sleeping on your back while pregnant isn't recommended as it puts pressure on one of your main arteries to your heart. As for the pressure in your tummy I'd ask your doctor! :)

Sorry, lol. When you're pregnant, your veins naturally swell, therefore they are called varicose veins. Thats why, as you get farther along, you'll be able to actually see your veins every where. Its just natural swelling, and it makes getting comfortable a hard thing to do. So when you lay a certain way, it presses on those veins, causing discomfort.

can you be a little more specific @taija

Probably from varicose veins.

really why not, oops I always lay down after I eat.

I have the same thing. They say while pregnant it isn't good to sleep on your back. And not to lay on your left side 30 minutes after eating. I am not sure why but my right side is most comfortable as well.