Sorry to hear, Sunny. I also have problems getting to sleep for same reason, though I'm so exhausted, once I fall asleep I usually stay that way. I do use two pillows. Maybe try getting less sleep? Seems crazy, but it does work for me. Unisom and Benadryl can also help.
I also use a humidifier all night which helps with the sore throat issue in the morning.
The lower back pain is probably not caused purely by propping up. It's probably all your muscles being strained by the growth of your stomach. I'm in physical therapy and do a lot of abdominal exercises to strengthen my core. The therapist says this should help relieve back pain (and pelvis pain). And do treat yourself to a massage. Either recruit OH, or get a prenatal one.