Let's play a game. You'll need your imagination, and if you really want to get into it, a basketball and some duct tape.
First off, pretend you are 37 years old. You have 4 children ages 4, 6, 9 and 11. They are wonderful kids but they are still kids - meaning they will make you tired.
This is where the duct tape comes in. No, not for the kids this time.
Place a basketball on your stomach. It doesn't need to be fully inflated... not yet... you have 3 more months to inflate it to maximum capacity. Tape it on your stomach, nice and snug. It's not going anywhere for awhile.
Lay down on your back. Oops, that doesn't feel so good, roll over to your left side, since that is what the doctors say is best for you now. Ah, that isn't too bad. Fall asleep for a few hours. But now your left hip hurts. And the knee. Ouch. With that 10 pound basketball still taped on, try and roll over to your right side. No, you can't flip onto your stomach. Oh, and try not to wake your spouse as you do this. Settle down for a few more hours. Half asleep now, scoot over in the bed so the 4 yr old can climb in next to you.
Imagine the household waking up now. The kids getting their breakfasts, etc. The spouse getting ready to leave for work. Somehow you have to get this body and basketball up out of this bed now. Twist, nope, turn, nope, swing the legs over and push up with your arms. Phew. Made it this far. Sit for a minute a find the energy to stand. Place your hands against your back that is not quite used to sleeping that way. Waddle into the bathroom until your muscles memory kicks in again and you remember what it is to walk and not ... waddle.
Enjoy the rest of the day.