Answer: Your doctor did not provide an adequate answer to your question, perhaps because she did not know the appropriate answer. Instead, she told you not to worry about it. The problem is, you are worried about. At nineteen, why would you want to wait any longer?
Unfortunately, I do not have a simple answer for you either, but at least I am willing to admit it.
It sounds like you are reaching the plateau stage of sexual arousal, but are not able to experience orgasm.
Learn to relax, and breathe deeply throughout your sexual activities. Use the vibrator on or near your clitoris, not in your vagina. If your clitoris is too sensitive, place the vibrator against your outer labia. If this is still too much stimulation, place a folded cloth between the vibrator and your vulva. Breath and stay relaxed.
Get your brain involved. Develop an erotic fantasy, look at erotic pictures, or watch an erotic video. Watch your boyfriend masturbate, as you do the same. Do not think about having an orgasm. If you are thinking about having an orgasm, it is less likely to happen.
Try clitoral, nipple, vaginal, G-Spot, or anal stimulation at the same time.
Get the book Sex for One: The Joy of Selfloving by Betty Dodson and read it with your boyfriend. Better yet, get one of her videos so you can watch another woman masturbate to orgasm. Seeing another woman have an orgasm may help you to have an orgasm.
Do not over value orgasm. Sex, solo or with a partner, should be pleasurable regardless of whether orgasm occurs. Learn to enjoy your own touch and that of your partner.
It is probably not in your best interest to explore vaginal intercourse until you learn to have an orgasm through manual or oral stimulation.