PLEASE RESPOND Toddler has green stool and complains of pain

My toddler has been having issues for about a month with pain going to the bathroom (he is fully potty trained).
About a month ago he started wetting his pants and pooping in them but right before this would happen he would say I have to go to the bathroom when we would get there he would say forget it.....he would start screaming and then go right in his pants. He would say his butt hurt and inside the hole of his penis hurt . Took him to the Dr. and he had to have an anal check and the Dr. said he was constipated. So he was put on mineral oil for 2days, and when he was done with that he was put on MiraLax for a month once a day. Dr checked him a week after his first appointment and said he was all cleared out.
    So my problem is, is that he still cries and complains of his butt hurting and sometimes his tummy. His stool has been green for atleast a month (I mean always green)..no change in diet. Also yesterday when he was complaining about his but hurting he went in his pants again. Should I be concerned? Should I take him back in? Any suggestions of what could be going on?

[s90]

http://www.greenstool.org/is-green-stool-something-to-worry-about/

http://*****************/question/index?qid=1006010104116

hope that helps.

[kc0409]

thank you!!