Hey moodyteen,
Welcome to the boards!
In terms of locating different parts of your vulva (vaginal opening, labia minor or "inner lips" etc.), I think a great place to start would be to check out this piece:
Innies & Outies: The Vagina, Clitoris, Uterus and More. Can you share a bit more about what your experience looking in a mirror was like? What were you able to locate and what were you unable to locate? From what you have written it is quite possible that you have located your vagina, and that it was dry and inserting something inside was painful. The vagina is not always wet and open!
The vaginal canal changes size depending on your level of sexual arousal. When someone becomes turned on, it expands in both width and length, and also often produces lubrication. So, once you locate your vaginal opening, one thing to try would be to explore your vagina when you are aroused. In addition, using extra lubrication helps! And, like you said, when you are nervous or stressed your muscles tense up! So working on putting less pressure on yourself, talking it slowly, and creating an environment where you feel relaxed will also be helpful in making vaginal insertion not painful. Have you tried any of those strategies?
If you want to read more about those ideas, check out this advice column:
http://www.scarleteen.com/article/advic ... hould_i_do
There are also some different vaginal conditions that make putting something inside the vagina painful or impossible, and a gynecologist would be able to rule those out for you.