Breastfeeding Child Having Abdominal Pains, Crying And Passing Frothy Stools. How To Control It?

Hi, My name is Denata and I have a 3.5months old son. I am breastfeeding him, but it seems that he is having a very difficult time becuase of abdominal pains, especially during the night. He is crying for over 3hours in a row. Controling his diapers I notice that he is having frothy stool and this is when his condition seems to be agravated. I have stoped taking milk in my daily diet, but I am having a lot of cheese and yogurt. I need to understand what is causing the troubles to my son. I was suggested from our pediatrician to try the diet of hunger for 24h, feeding water and some starch based food (starch boiled with water and a little sugar), after this he got improved, but after 2-3 days my son started again complaining and frothy stool? Please help me understand what is happening and what to do? Thank you very much in advance for your help.