PDDNOS child urinating in inappropriate places

I need some help. I have an 8 and a half year old son who has PDDNOS w/ autistic and Asperger's features, dyspraxia, expressive language disorder and just received a diagnosis of boderline to mild MR (total IQ of 60).  (This IQ test was done without his Concerta and I'm unsure of the results.) Recently (within the past 2 weeks) I discovered that my son has been urinating in his bedroom. His bed was completely dry and clean. The first time I found urine, it was on a throw rug in the middle of the room. The second time, I found urine on a beanbag chair, which was cold to the touch, I asked what it was and got a shoulder shrug. I asked again if it was urine and he stared at the ground and gave the bathroom excuse. I was very upset and took the chair and put it in the shower. (The throw rug wound up in the garbage becuase I don't have a carpet cleaner and felt that was a suitable punishment at the time.)  I'm considering throwing away the beanbag chair also, and not replacing it. I don't know what to do next at this point.  

Both times, I found something blocking the door in his bedroom that tried to prevent someone from coming in. I have no idea what has happened in the past two weeks with this child. To my knowledge, there has been nothing traumatic or different in the past month or so. Back to the problem. This past incident just about sent me over the edge. We rent a very nice house in a very nice neighborhood with an excellent school that has been more than accomodating to my son's IEP and special needs.  Our landlord does not allow pets in the house because previous tenants trashed the place and a dog died in the garage of a heat stroke. I'm worried I will fail my annual inspection with the landlord and lose my house due to this new destructive behavior my son is exhibiting. How can I handle this?