I think the best thing you can do for yourself is move on. I was kinda like you in my first relationship, and the girl actually did break up with me for the exact same reason as your ex's (we hugged once). I didn't read too much but Im guessing this is your first relationship? In which case you really need not worry, your first few aren't going to be the best, and looking back on them they will seem horrible. I really dont suggest waiting till you find that special someone, you gotta get yourself out there, get some experience with girls, not saying to do things you're not comfortable with, if you don't want to make-out or go anywhere sexually till you've found someone special that's your thing. But really you just need to get experience with dating and learning how to be a fun person in a relationship, because, not to be rude and really hopefully not say anything that'd hurt, the girl you were dating may not have thought you were that fun of a person to date.

You don't need to stop talking to her, or anything like that, you just need to understand that maybe, and most likely that guy she's dating now has had prior relationship experience and is able to comfortably kiss/make-out because he has done it before. And if it's that she's your ex and you have feelings for her, get over it, it may be hard or take awhile but if you plan on going into another relationship you really can't still be missing that girl. Theres tons of other nerdy fishes in the sea that I'm sure would love to date a cool nerdy guy like yourself.

TL;DR: Don't hold anything against yourself, its all about getting experience and moving on. You'll have some relationships you really liked, but its best not to feel bad about them and just keep moving on.