i am currently 28weeks and i understand how you feel .. sleeping sideways is best but not the most comfortable position to sleep when you have backaches .. when you need to change from left side to right side, feels like a struggling whale .. i use pregnancy pillow, make sure there is a firm support behind your back, this makes it slightly bearable .. however, at times pregnancy pillow still doesn't work .. somedays it is a miss, i still feel achy and uncomfortable .. i'll sleep with 2 soft pillows to elevate my head and my back doesnt lay flat .. or you put a normal soft pillow ontop of your pregnancy pillow, that works for me too . good luck.
Maybe try to get a body pillow and cushions to support u. i have a body pillow and a bolster to hug both sides. i also have a very small cushion to rest my belly. it worked for me. i take some time to get the right spot.
Use bolster and pillows to support your spine. Try stretching and pregnancy yoga too.
use pregnancy pillow!!