Oo, ni Braxton Hicks contractions lah, memang common around 26 weeks, especially bila you're lying on your side atau after rubbing your belly. One of my mum friends said the same thing happened to her, hilang after a few minutes je. But since it's affecting your sleep and comfort, definitely mention it to your doctor or midwife at your next check-up, okay? They can confirm everything is fine and maybe suggest better sleeping positions (pregnancy pillow really helped me!).