Brief Answer:
Is normal during pregnancy.

Detailed Answer:
Hi dear and thanks for your query.

Back pain during pregnancy is very known symptom, but the good news is, your baby is growing. That's exactly what should be happening -- but it can still be tough on your back.

Pregnancy back pain typically happens where the pelvis meets your spine, at the sacroiliac joint.

There are many possible reasons why it happens.
Here are some of the more likely causes:
1.weight pain
2.Posture changes.
3.Hormone changes.
4.Muscle separation.
5.Stress

You have done very good with heat pad but I will give to you some more tips .
1.Exercises(walking,swimming)
2.Improve your posture.(sleeping on your side with a pillow between the knees will take stress off your back:when sitting at a desk, place a rolled-up towel behind your back for support; rest your feet on a stack of books or stool and sit up straight, with your shoulders back.)
3.Be happy and think positive

All the best

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