I'm sorry, but I need to give some tough love here.
This is contradictory. Do you want to focus 100% on your business or your 20's?
I call it BS. Nobody ever focuses 100% on their businesses or anything else for that matter, with the exception of geniuses like Elon Musk.
When I was focused on getting my business off the ground, I still had time for my girlfriend, still hanged out with friends, practiced sports, and enjoyed my life. And I still managed to build a high six-figure business.
Don't fall victim to the myth of an overworked entrepreneur. If you don't have time for anything else but your business, it means that you don't know how to organize your time and be productive.
You're making excuses. Your girlfriend didn't limit your independence or made you waste time. You need to realize this now while you're still so young. If not, you'll always blame your partner for your own shortcomings.
Maybe she wasn't the right person for you, but don't blame her for your procrastination. If you were on a diet and somebody put a slice of pizza in your hand, would it be their fault that you cheated? Ultimately, it's your decision to eat it or throw it away. Granted, it's better not to have such people around (particularly if they're doing it because they want you to fail), but you
are being a dick if you blame them for your own lack of self-discipline.
The person you are with, unless they're literally keeping you chained somewhere in a basement, aren't limiting your independence - particularly if like in your case, it's a person you love who seems to support you. Obviously, this would be different if they were unsupportive and didn't want the best for you but I assume that wasn't the case.
@Spicymemer45 gave a good example in this thread. Hundreds of thousands of women would do all kinds of nasty things with Conor, but he understands that nothing will ever match the loyalty and support coming from Dee.
As for moving across the country, it looks like a purely hypothetical situation just to make an excuse. If you wanted to move, there would be time to worry about the impact of this decision on your relationship and possible solutions.
You're 20. There's no wonder that you're afraid of commitment. Moving in together is a big commitment, no matter how much you love the other person. It's not about her, it's about you not being ready for it - and there's nothing wrong in it. Anyway, you didn't have to live with her, you could have gotten your own place and invited her from time to time.
This one is the biggest excuse in the entire thread.
You're a male. You will
always feel like you're losing out when seeing an attractive girl, no matter how attractive your girlfriend is. Don't fool yourself this feeling will ever disappear (okay, actually it will, probably somewhere around your 70s or 80s). A grown-up male will acknowledge the beauty of the stranger and exert his self-control to realize that the brief, ultimately meaningless satisfaction of his primal urges isn't worth losing his long-term partner.
If you want to be 100% focused on your business, don't fool yourself that you'll be able to do so if you're constantly chasing meaningless sex with strangers. This is much more time-consuming and energy-sapping than being in a relationship.
Decide what you want in life: to build a successful business that will make you free or to let your primal urges enslave you. I don't know about you, but to me the feeling of freedom upon reaching financial independence is worth soooooo much more than having sex with hundreds of women. Personally, if I had to choose, I'd rather be wealthy and asexual than be a broke womanizer whose life is controlled by a stupid boss.
As for the second part about building confidence, etc. - nothing prevents you from doing so in a relationship. Yes, you won't be able to improve your pick-up skills if you want to stay faithful, but it's only one way of building confidence. You can get into sales, learn public speaking, volunteer, join social clubs, and do all kinds of other things to improve your social skills and grow. Then there's also immense personal growth you get from being in a relationship which IMO is much more valuable than the ability to chat up a drunk girl in a nightclub and make her go home with you.
I think that the thoughts in your head are right. But it's no use crying over spilled milk. Even if it wasn't an entirely good decision (in the end, only you can judge it), you can learn from it and make better choices in the future.