Sleep position question...

I know that you're not supposed to sleep on your back later in pregnancy because of issues with blood flow to the baby, however does anyone know of it being unsafe to sleep straight with a slight incline of pillows behind your back? I am finding side sleeping so uncomfortable lately even with pillows every which way and its so frustrating...I was able to get comfortable laying straight but with 3 pillows behind my back- I changed positions pretty soon though too concerned of potentially harming the baby....any help is appreciated!