You are 21 now so you are an adult and you don't have to tell your parents about this. I recommend that you find a woman gynocologist and perhaps meet with her to explain how very difficult it is for you because of what you experienced.

If you are struggling so much about this it may be better if you postpone it for a year even, until you can find a way to at least feel more comfortable with perhaps a woman gyno. A pap smear is to make sure you are healthy and it's a very quick procedure.