Pregnant and Breastfeeding

Hi everyone! I am currently 20 weeks pregnant and my toddler still nurses now and then, more so during the night. She has been on formula as well. She tolerates it well with formula but a few days ago, we noticed that she have been having runny poops. her diet hasn't change so I'm not to sure what's wrong. any pregnant mummies going thru the same thing? is it possible that my milk has changed(to colustrum?) #pleasehelp #advicepls and is causing the diarrhoea? thanks in advance!