generally the medicines no longer present any risks of fetal malformations after the 3rd month of pregnancy
. However, the pregnancy in your case deserves a keener attention. You can t stop the drug because its going to have other repercussions on you and in turn the child.
Continue your treatment on only modify your treatment with recommendation from your gynecologist and gastroenterologist. You can continue Mesacol
For now, no worries,
Hope this helps,