15 weeks pregnant, feeling pain.

Last Friday was may last check up, accrdg to my OB, yung placenta ko daw malapit sa bukahan. Earlier today, after I prep mg toddler for school, matinding pagod and mejo mangalay sa puson part ko pero walang pain. Now, bigla ako naka feel ng parang kurot sa may puson na part sa left side. Di ko alam if may connect ba to sa sabi ni Doc. Bearable yung pain, nawawala siya. Biglabigla lang sunasakit tapos mawawala. Normal naman may sakit2 na nararamdaman? Should I be worried? TIA!