okay so i always have aches and pains how will i know if im having real contractions like got out of…

okay so i always have aches and pains how will i know if im having real contractions like got out of bed and felt a really wierd pain in my butt like as if i had to poop really bad but i dont now have like a dull pain in my pelvic area. i tested positive for strep b so if i have contractions i need to go in but idk how to tell real from fake.