I believe that the standard definition virgin is "one who has never had sexual intercourse". That being said, I would personally suggest that there are degrees of virginity just as there are degrees of anything else. That being said, the real issue is that you have feelings of "regret" which tells me that you were uncomfortable having this level of intimacy at this point in your life.

The best thing to do now is simply to back track and set some clear boundaries that you will not cross until some point in the future and guard those boundaries tenaciously. You cannot change the past - you can only change the present and by so doing, change your future.

Grace be to you and look forward to a bright future.