Regrets about not dating enough

Hello,
I have a bit of a problem that I hope you can help me with.

First, to give you a little background:
I’m a 35 year old guy, and I never really dated much. When I was in highschool, I was too self-conscious to even think of asking anyone out because I had a very severe case of acne all over my face. That problem lingered into my college years, and even though I am very lucky in the sense that it eventually cleared up towards the end of college and left no physical scars at all, it DID leave psychological scars that kept me from dating for my remaining years in college and quite a while afterwards.
Eventually I tried dabbling in some online dating, and I struck up some really good online connections, but whenever I met these women face-to-face, it never went anywhere (we’d grab a coffee, chat for a bit, shake hands, part ways, and that would be the end of it.) You may find this hard to believe, but I’m NOT actually a hideous troll. The problem, I believe, is that I was a man in his mid-late twenties who had zero dating experience, and therefore also had pitiful self-esteem and a whole lot of social awkwardness.
I gradually got over that. I put dating aside and focused on just trying to make myself better. I picked up new hobbies, started taking more pride in my appearance, exercised a lot more, learned to cook, etc, etc, etc. And my sense of self-worth shot up quite a lot as a result.
I then dipped back into the dating pool, and soon met a woman who apparently liked this new me quite a bit, and we’ve now been together for several years.

Here’s the problem– I sometimes feel like I missing out on life by not having had more relationships. I’m not just talking about having sex with more people (though I’d be lying if I said that wasn’t part of it), but more importantly, I sometimes really feel like I just want to know what a relationship with someone else would be like. It just feels like I missed out on a huge part of life by never having been with anyone else, and I feel like I can’t even really judge my current relationship properly because I have nothing to compare it to. On the other hand, my girlfriend and I have lots of fun together, hardly ever argue, etc– so I feel like I’d be a fool to toss it aside just to satisfy my curiosity about what else is out there.
Adding to the problem is the fact that my girlfriend likes to joke about my situation by saying things like, “Just think, I’m the first woman you were ever with, and I’m the ONLY woman you’ll ever be with! Haha, you should have played the field while you had the chance!” I know she’s saying it to tease me, but it always triggers some really deep-seated feelings of regret.

Your thoughts?
Thanks.