Anak, please see your doctor or go to the hospital right away if hindi ka sure, better safe than sorry lalo na sa ganitong stage ng pregnancy. Ang sakit ng puso na may tigas ay kailangan talaga i-check ng professional, hindi dapat i-ignore.
A few of my mum friends had similar concerns at that point, at ang doctor nila agad na-check kung normal contractions lang or something else. Kaya please don't wait, go na, ha? Sending you love.