Constipation. Should i use suppositry?

Hi doctors. My 2.5 years son has been suffering from constipation for the long time since 1 year. Actually he passed stools once in 2 days. And it takes arround 10-15 minutes to pass potty which is hard approx 10-12 cm long and thick dark colour . And he keeps running here and there feel helpless and suddenly boom pass 1 stick that's over. So i started dulcoflax child suppository which is dived into three parts and i every day insert 1 part in night and he passed within 15 minutes and same he runs and passed same manner and same consistency. I tried for three days. I used 1 suppository for three days and he passed in 15 minutes. But long stick type daily. But I stopped yesterday to check . So he didn't pass poty and today till not passed. What does it mean?? I doubt his intestine size enlarged due to this his urge is not increase to pass pooty. Now it is empty so storing potty to fill . If i am right , then how long should I use suppositry? And how to control this situation. pls help