I'm worried!

Doctor told me at anatomy scan that my placenta is close to my cervix. She didn't seemed too concerned and said as the baby grows my placenta should expand upward and not cause any issues. I have to go back at 28 weeks for another US and they told me no intercourse until this is resolved. At first, I didn't think much about it because the dr didn't seem worried but I'm kind of freakin out. Anyone else have this problem or been through this before?