Ah, anterior placenta! A few of us in my mum circle have it din, and honestly ang advice na nakuha namin from our OBs is na pwede lang talaga most positions, kaya don't stress too much about it. Side sleeping (left side is usually preferred anyway para sa circulation) worked best for most of us, but really the best position is whatever makes you comfortable, kasi stress din yan sa baby if you're uncomfortable the whole time, hirap mo matulog. Since every pregnancy is different though, I'd suggest double-checking with your OB din kung may specific concerns sila, just to be sure!