Hello. Yes, you must consult your physician for these symptoms. Constipation in third trimester of pregnancy is common due to compression of rectum from gravid uterus. Laxatives causes diarrhea because this was not true constipation and lead to onset of diarrhea. Another possibility of having vomiting and diarrhea is gastroenteritis i.e. minimal inflammation of stomach and small intestine due to food allergy or poisoning. This lead to dehydration which require prompt treatment in pregnancy. Mainstay of treatment is - drink adequate amount of water, medication to control vomiting, if dehydration is moderate to severe then it need to be corrected with IV fluid support. Hope I answered your query. If you have any further doubts, I would be happy to help you. Have a good day!