你小时候有没有打过结核疫苗？
Most of people from China or a lot of other foreign countries will have positive ppd because of TB vaccine we had. Since your x-ray was normal, the doctor at your school should easily rule out TB in your case. I don't think it is correct to still have you take INH. You can discuss with another doctor and get a second opinion.
Don't worry, your positive ppd will not affect your reproductive health at all.