Trouble Sleeping

     I'm 18 weeks and 5 days pregnant with twin boys! Recently, I've been having trouble sleeping. First, I start on my left side then throughout the night I switch to my right. Lately, the only position that's comfortable is on my back. I've read that's not a great position to stay in throughout the night, but sometimes it's the only way I feel comfortable.  My arms will fall sleep and my thighs hurt from laying on my sides too long. I do sleep with a couple of pillows between my legs. Any suggestions would be great!