Help Kinda confuseed

So I had sex for the first time on February 11 (btw he pull out and make sure it wasn’t cum in me and on me) after that i was fine since then my stomach been hurting on and off weirdly and I’m also on birth Control and I take my pills everyday This app said i suppose come on my period Yesturday but idk if I’m on or not bc I’m cramping do you think I should be worry my friend said it probley my body going though changes bc it was my first time having sex 🤦🏽‍♀️