Thank you for your post. First of all, you're obviously not a monster. Your ex hasn't said that and I don't think that. She has said you made her feel uncomfortable. I totally believe you when you say it wasn't intentional. From my own experience I know that it is possible to confuse seduction with pressure and even if you've internalised 'NO means NO' at a young age this can be a way to excuse to yourself trying to move things forward in the absence of a 'NO'.
This isn't necessarily to say you didn't do anything wrong. I did. It seems possible you did. But it doesn't automatically make you predatory and certainly if you're still under 25 (or so) your brain is still changing and developing and you can learn and grow from this.
I'm not going to lie - it's frikkin' hard. Seven years later I still feel guilty everyday and I suspect that's something I'm just going to have to learn to live with (which slowly, I think, I am doing). **But that doesn't mean I don't deserve continued existence.** An okay, manageable life
is not the end of the world. It
is possible to continue living without feeling happy or free all-the-time, or even most of the time. The important thing is to put good back into the world.
As said, I believe it is certainly possible that you didn't even have the faintest inkling at the time that something was wrong. If your gf literally gave you no indication that there was anything the matter I honest do not feel I think it would be unfair to blame you for what happened. That said, I think one can generally have -some sort of a sense- when one's partner is even a tiny bit unsure or sleepy or uncomfortable, even if they might be anxious about saying so, or are acquiescing or going along with something cause they don't want to cause a fuss. I think there can be a lot of reasons why a young woman might do this - not only fear or anxiety, but because women and girls are taught generally to be quiet and not to contradict guys and to generally be peace-makers. Plus, at the time she may have simply wanted to please you, make you happy, or might have felt obliged. Like, a lot of complex stuff could have been going on! Obviously I can't speak for your ex and wouldn't want to.
Basically IMHO it sounds as though you were clumsy and not wholly self-aware... which means you, sadly - acted like a lot of young men (younger me very much included). I don't want to minimise the seriousness of boundary violations or anything that might be considered sexual harassment or assault by saying this, since something being relatively common doesn't make it "ok", but I strongly suspect such behaviour in relationships between young people/ adolescents happens more than people would like to admit or want to see. There's an enlightening but kinda upsetting study by Struckman-Johnson et al. from 2003 that looks at this:
http://www.jstor.org/stable/3813772They looked at what they called "postrefusal sexual persistence", defining this as "persistent attempts to have sexual contact with someone who has already refused" - sexual harassment by any measure and sexual assault by most. In your case I do not know whether your gf has said anything to ever indicate she wasn't in the mood or was uncomfortable like "I'm feeling sleepy" or "let's just snuggle" but this is the kind of stuff they're talking about.
They found that 40% of the 275 men and 26% of the 381 women interviewed admitted to this kind of abusive behaviour.
So, while this doesn't mean you didn't do anything wrong, it does suggest there is a serious problem in society when it comes to people crossing lines in the name of "seduction" and it's messed up. Reassuringly, it is probably not something the majority of men (or women) have done, but it's also not 0.1 of the population. And I think the best way of responding to that, even - or especially - if you've been called out by an ex or feel vaguely concerned or worried about your own past behaviour is
to educate others.
Interrupt and don't laugh at rape jokes. Talk about enthusiastic consent. Maybe even give out leaflets on learning good consent (I've done this quite a few times and it's always gone a lot better than expected). Basically, try to be part of moving things towards positive change. Because I don't think you're evil or a monster. I think you're a sincere, reflective guy who is worried they hurt someone they loved. And there are worse things to be than that.
So yeh, in future, make sure you always practice verbal, enthusiastic consent i.e. only proceed if you're 100% sure that your partner is happy, consenting and into it; ask before you move onto something new (I've had an ex - not maliciously but somewhat thoughtlessly- try a completely new sexual thing on me we'd never done before without asking and I wasn't traumatised, but I was pretty uncomfortable. I absolutely wouldn't call them a monster); just check in and be alert to what's going on basically.
And if you ever feel like "I'm worried that we haven't been intimate for weeks" or "this is the last night I'm going to see her for months" or "she said she wanted to cuddle, but if I take it slowly I can escalate it into something sexier and that's seductive, right?" or "This is just what we need last night and she seems to be going along with it, though I wish she were smiling more... I think it's okay though" stand back, get out of bed and take a cold shower.
But really I think you know all of this already. So, it's not even info directed so much at you, just to any other guys reading to know this stuff wasn't already really obvious!

As for supporting your ex and making amends as best you can, obviously give her space and distance.
I would also
highly recommend reading this two-page leaflet called entitled 'What to Do When Someone Tells you that you violated their boundaries, made them feel uncomfortable, or committed assault' (catchy I know!) because it's great and is easy to follow and gives you clear steps as to what you should do.
http://www.phillyspissed.net/sites/default/files/what%20to%20do%20when%20someone%20tells%20you.pdfAssaulters are not villains. They/ we are not doomed. We are humyn, and how we address these situations (and ourselves), after being told of it, makes a Hell of a difference. Literally.
Please read it and I genuinely hope it's helpful.

Kind regards,
Sprock