Frequent diarreha after delivery. This?

Hi I have delivered a baby 11 months ago. During delivery I had severe diarreha 1 week before delivery and 1 week after delivery. After that also like at least month thrice or 4 times I have diarreha. Sometimes it may be due to some food I eat but none of my family or friends who ate with me have their stomach upset only I have. Some times I would have eaten plain food like everyday still I have diarreha. It's very problematic stomach growls as if something is moving n I need to rush to washroom. It annoying and embarrassing as it happens in office too. So I take lomotil tablet when I have diarreha. Earlier I never had this type of issue. Post delivery only my gut has become so sensitive and I'm not any food outside only scared of this. Anyone can help what i need to do. Which doctor I need to visit and any tests are needed for this ? Please suggest.