Saru,
I have actually traveled to Nepal when i was in OPT last year and i had not even gotten my  OPT card by then. I had even asked some immigration official in the airport immigration dept before i got the tickets and she told me as long as your visa is valid u should be good to swing in n out. However while entering US, they took me to the secondary passport checking room where the immigration officers did scrutinized and checked all the details of my info in their system,(it was lill scary ofcourse) but they didnt bother me too much and let me go.
But you need to make sure u have a new valid I-20 and travel document from ur International student office made.
It worked for me, hope its the same for u..goodluck