Back pain is pretty common during pregnancy.Your body is carrying a lot of extra weight and your back, unfortunately, bears the brunt of it. 
However, these seven tips should help relieve and prevent any pain:
Wear proper shoes
Make sure you are wearing proper footwear at all times. Only wear shoes that have a proper insole or good arch support and avoid really flat or really high ones. Try to find a middle ground that offers both comfort and support.
Don’t sleep on your back
Sleeping on your back is not recommended during pregnancy anyway as the weight of your uterus can press on a major vein carrying blood to your heart. When it comes to relieving back pain, sleep on your side with your knees bent and use a pregnancy pillow if you have one.
Stand up straight
Standing up straight and maintaining good posture goes a long way to ensuring you don’t hurt your back. As your bump grows bigger you might compensate carrying the extra weight by leaning back slightly. Try to avoid this as it can actually put more strain on it.  When standing up, keep your feet slightly apart with your shoulders back and relaxed.
Go for a swim
Swimming is great as you can feel almost weightless in the water. Enjoy an afternoon of leisurely floating around your local swimming pool or why not sign up for prenatal aerobics class which will help to relieve any pressure on your back.  
The cat stretch is great for stretching your back and relieving any tensions. Simply get on the floor on all fours and breathe in as you arch your back. Slowly and gently relax the arch as you breathe out.  
Go for a walk
Walking is low impact and will help to relieve any tensions and loosen up your back. Make sure you are wearing proper footwear at all times when exercising.
Slow movements
As your bump gets bigger, you should avoid any sudden movements and gently ease yourself up and down. When lifting things you should always lift with your knees and not your back.