Khloe Kardashian Undergoing Fertility Treatment

Sources connected with Khloe and Lamar Odom tell TMZ ... they have tried in vain for months to get pregnant. So Khloe went to ART Reproductive Center in Bev Hills Monday ... to start the process.

With Kim Kardashian by her side for moral support, Khloe gave up some blood so the docs could evaluate her hormone levels. She's waiting for the results, and will then get a stylized treatment program.