going to the loo(ds1)

I cant find a health forum so im posting this is here if thats ok,brandon has always had probs going to the loo ever since he was one, he is always constipated for 2 days then he gets diarrhoea for 3, i was forever at the docs and they gave me stuff for him all the time, and constantley asked about his diet, he is always eaten a fibre filled diet, he saw a specialist and they put it down to a anal fischer, he had a op on it and was ok for awile, but then went back to this, he is 6 now and its not fair on him, he is having time off school cos he cant go and we have to stay in for days, i have took him to the docs again for 2 yrs but they are not listening to me, they keep giving me lactolose, he cant have that all the time!!!! i have a appointment at the docs tomorrow, i really dont want to go cos they dont listen, they will fob me off with more medicine, the symptoms he is having sound like irritable bowl sydrome, can kids get this?
Any adivice would be great thanks i just dont know what to do anymore for the poor little guy 😢