Can't get off

It's unfortunate, but the TLDR answer to your query is that it is common for young women to have problems reaching orgasm. In fact, surveys have found that ten to twenty percent of all women have never had an orgasm.

That doesn't mean that all those women will never be able to have one, just that they haven't yet figured out how to do it.

Guys are lucky in this department: we're born with this thing sticking out in front of us that's conveniently at hand-level, and most of us start fiddling around with it as soon as we're able to control our hands as infants. Since it feels nice, we keep messing around as we grow up, and because the male sexual response is pretty mechanical, sooner or later we have an orgasm.

The female sexual response is much more complicated, and what's going on in your head will have a much larger effect on your ability to come than what's going on in a guy's head when he masturbates or has sex.

Since you say you can get close to having an orgasm, it sounds to me like there's nothing physiological wrong: your brain is capable of letting you feel sexually aroused (something that some medications block), and the neural wiring between your clitoris and your brain is all functioning normally, so you're able to reach what's called the plateau phase. But then something blocks you from breaking through to orgasm.

It's most likely that what's stopping you is psychological barrier of some sort, and you might have to do some work to identify what it is and figure out how to overcome it.

I suggest you consider reading a couple of books:

Come as You Are by Emily Nagoski covers the female sexual response as a whole and discusses research findings that aren't widely known. It's a very positive book, and the odds are that you'll have a few 'lightbulb moments' when you read the book, and you'll end up understanding what you experience in sexual situations much better than you do now.

Becoming Orgasmic by Julia R. Heiman is another book many women have found useful. It's more of a program for discovering what you personally need in order to have an orgasm.

If reading books isn't really your thing, have a look at Betty Dobson's website: https://dodsonandross.com/index.php

Is this a recent development or have you never had an orgasm? And how much and how often do you smoke weed? If you're always stoned when trying for an orgasm, it could just be the weed induced time distortion which is making you believe an orgasm is impossible.