I Am Concerned About My 9 Month Old Son. Approx

I am concerned about my 9 month old son. Approx 4 weeks after birth, he started to have less frequent bowel movements. On average they were 7-10 days apart, but he once went 20 days with no BM. He has always wanted to feed very regularly. He was exclusively breast fed, and I fed him approx every 2 hours during the day, but at night he woke for feeds as frequently as every 45 minutes, he seemed very uncomfortable during the night and fed until he passed gas, then went back to sleep. He has yet to sleep through the night, sometimes he'll wake just 2 or 3 times, other times it's as many as a dozen. His BMs have been hard since he started on solids (at just before 6 months) he seems to struggle to have a BM. His BMs also have a strange smell. There is no problem with weight gain. He's in the 90th percentiles despite being 7lbs 9oz at birth, and neither myself or my husband are particularly big. Our pediatrician is aware of all this but seems unconcerned. Lactulose has been prescribed for constipation, but I'd rather treat the cause. Could this be lactose intolerance? I stopped eating diary for about 4 weeks when he was 6 weeks old but it didn't seem to make any difference