was it bad that I cheated on my girlfriend to experience other women after she took my virginity at 20 and had sex with 5 guys before me and had a threesome?

You cheated. There is no excuse that you could come up with to justify cheating on your significant other. You were wrong to betray her trust.

The phrase in your question that really tickled my fancy was "she took my virginity". The bi tch! How dare she do that. You tell her you want it back! >:-D

It might pay to do her a favour, and yourself as well. If you want to experiment with other women, break off the relationship and go out and have fun.  Cheating demeans both of you.

If you wanted to "experience other women" you should have been honest with her and broke up with her first. She has obviously told you about her experiences prior to your relationship....as far as your virginity goes.....it takes two.....she didn't "take" anything from you if the sex was consensual....seems you gave it up also, just sayin'

You cheated and that is bad. Period. It is not her fault that she was your first.

If her previous experiences bother you .. Then, you should have considered that before you entered into a commited relationship with her in the first place. 

Since you DID enter into a commited relationship with her there would be a reasonable assumption that it would be a monogomous relationship, and then you subsquently cheated on her? .. You bet that is 'wrong'. 

The truth is .. What she encountered before you, is her business .. At that point she had no connection or obligation to you ... However, after the fact, and knowing her past, you chose to commit to her anyway.  You were obligated to be faithful .. So guess what Einstein .. You are totally in the wrong... and that is very bad.

Cheating is never justified.  If you don't like her history then leave her, don't cheat on her.  SHE has done nothing wrong .. she is an adult and is entitled to do what she pleases while she is not in a commited relationship  .. You are entiitled to choose to be or not to be with someone with that kind of history ... you are not 'entitled' to cheat.

So sad that your have lost each other for now.

Who knows what tomorrow will bring.

Maybe respect and a time to learn.

Well, probably not good in terms of your relationship with her but it may or may not be a deal breaker.

At my age, LGBT is the only area I will still die without understanding or experiencing.

Had my first marriage lasted, I expect I may well have died after having experienced genital sexuality with only one woman. 

But without having that level of commitment, considerations of "morality" aside, I'm not sure I would have wound up acting any differently than you.

Certainly the timing is bad for you given the current relationship you seem to have with your girlfriend, but I suspect you two can work it out if you so choose.