I entered the country legally in 2012 on a J1 visa. Then a year later I changed it for an F1 visa. The F1 does not expire as long as I remain in school. However, I stopped doing school a year ago so technically my visa in invalid. I’m just worried about flying with my passport. I’m sure it should be fine. Even with no stamps. I just don’t want TSA to call somebody else over to check the passport, because that will raise more questions.