Is it normal to get 8 infections in a year for young adult in college ? is it a concern ?. infections such as cold, flu, gastrointeritis

Yes: In fact this is very normal, especially if you live in a dormitory where there are common bathroom facilities. The best thing you can do to prevent infection is get vaccinated for influenza and meningococcal meningitis (if you haven't already), wash hands before you eat and before/after using the bathroom. Avoid handshakes with sick classmates. Don't share utensils, supplies and use hand sanitizer