There are ligaments that hold your uterus in place and with the uterus stretching they stretch too making them easily agitated so when you sneeze it gives a sudden tug on the ligament and that's the pain you feel
I'm 10w and the same thing is happening to me, I've had pain on my right side since I found out but when I sneeze I could cry it hurts so bad sometimes. I did read that during pregnancy your uterus moves a little to the right so maybe there's a little more pressure there and it's sensitive.
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