@bhinsley Welcome to Mayo Clinic Connect! We're glad you found your way here.
Pain in your left flank plus the finding of a slightly enlarged spleen might be an indication of some sort of damage to that organ. Did your doctor followup with you on that? Have you had any trauma to that area from late February on, a rough game of touch football, auto accident, off-roading over extreme terrain, etc.? Just a thought...
I hope you get some answers soon that will alleviate your concern, and let me know what you find out.