I have rough time to concentrate during stressful situations since enter college like never before causing problems since now two years. can be adhd?

Possibly: Your doctor could do a screening test or arrange an evaluation to see if the symptoms are due to adult add/adhd. Many other factors can affect concentration. First and foremost is inadequate sleep. Excessive alcohol intake ranks high, as does anxiety and depressiion. Not as likely to be add if at least some of the features were present when younger some compensate very well so problems start later.

Possible: Severe anxiety can also affect concentration. If concentration problems are limited to stressful situations then it may not be adhd. May need help with anxiety first.

Hard to say.: If this truly just started two years ago, then adhd is quite unlikely. If, though, you did better in high school because family and other adults provided lots of external structure, than an assessment for adhd might be worthwhile. In any case, getting help dealing with stress might be a big step towards easing your difficulties.