Mama, that kind of pain at 33 weeks can mean different things, sometimes it's just Braxton Hicks or ligament stretching, but please don't guess, ha! Go see your OB as soon as you can, or if the pain is really bad or you're bleeding, go to the emergency room na. Better safe than sorry, especially since you're in the third trimester na.
A few of my mum friends had similar concerns around that time, at kahit "normal" lang ang iba, kailangan talaga ng check-up para ma-rule out anything that needs attention. Take care, at hoping everything's okay with you and baby!