Hey mama, that's most likely Braxton-Hicks contractions na, lalo na at malapit ka na sa due date, marami sa amin naka-experience ng ganyan around 35 weeks and it's usually normal lang, pero since you're worried, mas okay na i-confirm with your OB on the 18th, or you can even call the clinic before then kung tumaas pa ang frequency or if may other signs like bleeding or heavy discharge. Try to rest and stay hydrated muna, at kung biglang mag-intensify or mag-regular na, don't hesitate to go to the hospital na para ma-check agad. You're doing great, alam mo yan?