Best Position for Sleeping

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Hello ladies. So I'm 21 weeks along and I'm finding it difficult to find a good position to get to sleep.  I'm 4'11" so I'm all belly and showing more than taller ladies at 21 weeks.  I have had issues with chronic low back pain due to an accident I was in.  Because of that, I'm a back sleeper.  I know that sounds weird but in the past, sleeping with a few pillows to prop my head up and then a pillow under my legs has been the best way to sleep to help with the pain.  But now, it seems that nothing is comfortable for my back.  I have slept on the couch the majority of my pregnancy because it was more comfortable at the beginning.  I try sleeping on my back but slightly propped to the side because I have a pillow between my back and the back of the couch.  Then I have my head propped up a little and two pillows under my legs.  That doesn't work.  Then I try either side with a pillow between my legs and a pillow under my belly.  That doesn't work and makes me have to pee more somehow.  I also tried sleeping in our recliner and that didn't work either.  Last night, I had to take Tylenol before I could sleep. I know Tylenol is safe but I try to avoid it as much as I can because I have medicine that I have to take every day anyway and I want to avoid additional medicine as much as possible during this pregnancy.  
So, if you've had low back pain, what has worked for you?  I still have a little while to go and I get up way too early for work and I need my sleep.  
Thanks in advance!