At the time that Obama traveled to Pakistan with a college friend at Occidental, the US did not permit people with American passports to travel to that country.
He probably traveled on an Indonesian passport. He was registered in school in that country as Barry Soetero, Indonesian citizen (he was adopted by Soetero), religion Islam.
He most likely was registered in all of his college work as a foreign student, so received special grants or loans. That would also explain why he has refused to reveal his college records along with a real birth certificate.