7 year old son with fluid in his 3rd ventricle

Please help me, my 7 year old son started having daily headaches about 6 weeks ago, as they got worse i ended up taking him in to emergency. After many questions they decided to do a ct scan which revealed fluid in his 3rd ventricle. I was told he was fine to go home, but do get a mri soon. After weeks of going in circles and a ct scan, mri, ECG & then a lumbar punch or spinal tap, i still have no answers from the Drs as to what is wrong with him. He also has had loss of bladder control, rapid mood changes / swings, loss of short term memory and he is unable to concentrate on anything for more than 1 minute. It is impossible for him to learn at school, but he is still attending to keep busy while we wait for the drs. The drs have told me they are eliminating things meanwhile i am sure my son is getting worse by the day. No one is telling me anything as they keep saying everything is coming back clear, what does this mean.