as far as everyone knows, you cannot make a reentry in USA with your OPT card . But US government had some changes over this matter and if you are working in OPT, have your employers official written letter that you are an employee of that company with so and so remuneration, then you can go to nepal and come back...but you never know. without a valid US visa, you might never fly from nepal, or you may be denied re entry at port of entry. my fren did the same thing, he was refused to be boarded on plane in nepal...make sure with your international advisor. and ask him to clear this with USCIS.