The headache's are part of the very minimal side effects (for me anyway), nothing Tylenol can't take care of, it does say in the side effects on inhousepharmecey.com for dom, that headaches are common. As for the diarrhea, that is a very good question.. I have never put two and two together lol. I did notice I started losing weight from the frequent bathroom stops and it has eased up but my metabolism has kicked into high gear which is something that I needed either way. I hope more mommies on here can give more feedback because I certainly would like to know. So thank you newbie for asking and best of luck to you on your breastfeeding journey =)