Why do i feel presure when i lay down an am 28 weeks pregnant...?

Normal?: I presume that you mean you feel pressure in the pelvis? It is a common complaint as you get into the third trimester. If you mean pressure in your back or abdomen then try lying in a different position.

Pregnancy pressure: It's preferable to not lay flat on your back during the later stages of pregnancy. It's best to lay on your left side and not your right side. That is because of the large blood vessels to and from the heart and the sides of the body where they are. Constipation is common during pregnancy and may be contributing to your discomfort as well. Be sure to address your concerns with your Obstetrician.