How were you taught about puberty and sexuality? Did your mom or anyone sit down and talk with you about it before you got your period for the first time or was it a "surprise"? Did anyone tell you how sex happens? How did they talk about it? Did they make it sound scary or painful? Sometimes just learning about sexuality the wrong way can influence how a person feels about it. Telling them that it's going to be painful or making it sound like it's unpleasant could make that person anticipate pain. A lot of times, when a woman anticipates pain down there, her muscles will seize up painfully. It's called Vaginismus and it's treatable. It's like if someone tells you that getting a shot is going to be painful. If you tense up, it's 10 times worse.
I know you are scared and are just coming from a bad experience at the gynecologist's office, but is this something you want to fix? Do you want to be able to share intimacy with someone without having this fear? If so, there are ways to go about it. First, you need to be comfortable with yourself, inside, outside, and especially "down there." Talking to a therapist, whether it is a sex therapist or not, would probably be the most effective thing, if it's the right therapist. If you aren't ready for that, doing some reading about sexuality to get some correct information might help calm some fears and get you used to the idea of being sexual, even if you don't actually contemplate the actual act just yet. I know this sounds silly, but maybe even reading some low-key romance novels would help you think of sex as more of an intimate, emotional connection and less of a physical act. Just a thought.
If you aren't ready to start to fix this now, that's okay. You can wait until you are ready, but don't lose hope or build this up so much in your mind that you'll never want to try to fix it. There are a lot of people who are asexual, but that really refers more to people who have no interest in sex, which is fine. But I don't think that you think this is fine, otherwise you wouldn't care enough to post here. The fact that you do care and that you do feel alone in this makes me think that a part of you wants to fix it.