Jia you mama, you've come so far! I had very similar issues in my third trimester and sleeping was the biggest issue I faced for pregnancy. I also found sleeping on my left really painful and I slept more on my right. I completely cannot sleep on my back because I felt like I was suffocating :/
I used a big long bolster to elevate my torso and put between my thighs, as that helped to alleviate some back ache. As for the pelvic pain I try my best to do yoga stretches daily, cause for me it's more painful when I don't stretch and the joints are stiff. I had sciatica and I did have to use tennis ball to roll on the muscles. I also got my husband to massage for me, cause it was during circuit breaker and there was no massage services available at all. Hang in there, it does go away after delivery! Sending you love!