According to the data you provided, you are experiencing splenomegaly. Splenomegaly might be caused by several reasons: increased function, abnormal blood flow and infiltration. The low grade fever, muscle spasms, and insomnia might be related to infective disease. Benign or malignant infiltration is less probable since it would have probably aggravated by now.
The negative tests by the specialist for infective diseases might have simply not included the real cause. Additional tests might reveal the cause.

My son had ruptured his spleen five years ago, now age 12. He was riding his bike camping and flipped over the handle bars and landed on a bolder. The doctor had an embolism performed. He expained it as pigs fat to glue the leaking blood. He could not find the "holes". He had said that they were to small to show up. This incident took place in Austin. When we got back home to Houston the head surgeon had to perform a month later taking out his appendix and had said that he would have taken out his spleen. I am thankful that he did not. His now doctor recently had a ct done on him to just do a general checkup to see that things were ok and all. My son wants to play sports again but I am very scared of this. I cannot find anything pertaining to this on the web, as to what exactally was done to him, etc. His doctor now doesn't seem to knowledgable to this procedure. What can you tell me about this or what type of doctor, questions, should I have to ensure that he is alright. Or should I be always forevermore concerned about my son. I greatly appreciate any help that you might be able to give me pertaining to this. Many thanks and best of luck, MistyLK

Have you considered the possibility of Splenic Flexure Syndrome ? The low grade fever, muscle spasms, and pain in upper left quadrant are all typical symptoms of this.

I have the condition myself, with the above symptoms, plus shortness of breath. In my case the illness is caused by an inability to digest carbohydrates, and this causing trapped gas in the transverse colon.

I just started following a low carb diet, and taking digestive enzymes....am already seeing an improvement after a few days.

In some people Splenic Flexure Syndrome is linked to constipation, (though not in my case).

Have you considered the possibility of Splenic Flexure Syndrome ? The low grade fever, muscle spasms, and pain in upper left quadrant are all typical symptoms of this.

I have the condition myself, with the above symptoms, plus shortness of breath. In my case the illness is caused by an inability to digest carbohydrates, and this causing trapped gas in the transverse colon.

I just started following a low carb diet, and taking digestive enzymes....am already seeing an improvement after a few days.

In some people Splenic Flexure Syndrome is linked to constipation, (though not in my case).