I’m absolutely terrified of sex/intimacy

I’m a 19 year old woman, and have been thinking about sex a lot as I get older. I am a virgin, but also have very little relationship experience. It’s not that I have no sexual desire, because trust me, I definitely have sexual desire and get turned on and all that. But the idea of being vulnerable in front of someone like that scares me a lot. It doesn’t help that I feel very ugly and have a less-than-ideal body, so it is hard for me to imagine anyone could find me attractive, especially naked, but it’s more than that. What if I can’t finish? What if I can’t make him finish? What if I start crying in the middle of it? What happens after it’s over? How do I express all of these concerns with my partner?

I’ve been in one relationship before, it was with a woman, and she didn’t touch me at all, and was more or less embarrassed to be seen with me, so I definitely think that has kind of hindered my idea of intimacy. I am bisexual, and I feel the same way about sex with a man or a woman, just so scared and nervous.

I’ve had a couple situationship type of relationships, and when I’m with them, it was always just anxiety about sex and such, which eventually makes me shut the relationship down. I also think I need to be with someone more assertive than the people I’ve been with, as I hate initiating in any way. But I worry that I won’t find someone with the right balance of assertive and gentle and understanding, as again, I’m not the best to look at.

Is anyone else feeling this way? Everyone around me is just so okay with sex and I feel like I’m the only one who has anxieties and nerves regarding all of this.