reflux meds, probiotic, or formula?!

Melissa
My son has been on reflux medicine since Friday. I also give him gerber soothe probiotics in his first bottle of the day. He has been pooping A lot lately. He is in similac total comfort formula. Takes 4 oz every 3 hours. I'm wondering if the probiotic OR the reflux medicine is causing the frequent Bowles daily. OR is it the formula?! He is on radadine for reflux. 
 Thank you!