you don't have F1 visa, how

If you changed from H1 to F1 in the US, then you only have F1 status but not F1 visa. When you leave the US, you will need a valid F1 visa in order to come back. As I pointed it out earlier, it will be next to impossible for you to get a F1 visa, because your strong immigration intent. The only exception would be when you visit Canada or Mexico for under 30 days, then you can still come back without a valid F1 visa.