I would like to have sexual intercourse with the girl I love. But I'm really shy about it because I have scars on my back from cuts and such, they're really unattractive, and I KNOW she'll freakout if she sees them, what should I do?
Having sex with someone else is really intimate, and we're all vulnerable in that space, and double for both when we have strong feelings for the person we're with.
So, in order to make our own best choices -- including in terms of our emotional safety -- we need to understand that. Does this person have equally strong feelings about you? Does she treat you with respect and kindness? Have you any reason to think she'll somehow treat you poorly because you have scars (and many people do, some of us more than others, but we're not Barbie and Ken dolls, after all -- we're real people with scars, zits and all kinds of imperfections)? Do you think she's mature enough to deal with your scars or are you uncertain about that?
If she loves you, too, if she treats you with respect and kindness, and you have no reason to think she'll treat you poorly, or lack maturity, then the only question is if you feel ready for that kind of exposure and vulnerability. If you're not, then you either wait until you are, or you take an emotional risk and see what happens.
We all can ask our sexual partners or potential partners for things we need around this kind of explosure, too. You can talk to your girlfriend and let her know about this before you're sexual with her, which I'd suggest no matter what. That way, you can let her know how you feel about it, let her know what you need from her with it, and maybe even show her in a non-sexual context to make this less loaded for you both.
We do have to extend some trust in a person we're sleeping with, including trust in the fact that that other person -- and you -- are coming to sex together knowing it's real, not airbrushed. There are scars involved sometimes, or cellulite. People fart or belch during sex, sometimes. We sometimes have to share difficult history in negotiating limits and boundaries. That's the deal. If you don't feel you can extend that trust, or the other person hasn't yet earned it, again, waiting until those things are in place is probably the eway to go.
Same goes double if you're just not ready for sex to be as imperfect and human as it is, rather than some sort of performance, or way to impress someone else. Sex with someone else is about connecting, even when it's casual, in a pretty real way, so if you're not up to that kind of connection yet, hold out for when it feels more right to you.