Hi Mermaid,
Your doctor should be able to tell if your spleen is enlarged by a physical exam. This is not as uncommon in thal minor as many think. The pain may worsen at night after eating dinner, as there will be more pressure in the abdomen with a full stomach. The enlargement is caused by the destruction of red blood cells (hemolsysis) by the spleen. B complex and magnesium may have a positive effect on slowing this destruction. I would also suggest daily folic acid supplements, which are commonly recommended in thalassemia.