Happily married but always fantasizing about past girlfriends

If I'd of known then what I know now, I'd of taken a few of them up on it

Could not agree more. The time when nothing much more in the way of opportunities comes, comes far too quickly.

Having thoughts and dreams of past relationships, especially those that were a bit on the wild side, is normal. In my current situation, things are very vanilla and not likely to change and I don't want to end this relationship. But, I still think about those kinky times . And, I also fantasize about a women that I meet now and then and think about getting kinky with her.I even thought about getting enemas from my male chiropractor .

I know the OP is no longer on this site, but this at least is my take on this topic. I think its pretty normal to reminisce on previous relationships or sexual experiences, and its not necessarily an indicator of your current situation. It would seem to me that you think your life is objectively better with your current partner/spouse than with previous intimate partners, and (correct me if I am wrong) you don't have any pressing things you really want to change.

Most people really easily, when their attention wanders, wanders to the past. Its really easy to get stuck in "what ifs" or regret not having taken a certain path. Ultimately where we are now are the result of those choices or lack thereof. One therapist told me "regret is a tool to help you make better or different future decisions or actions". So maybe there is some regret, but clearly those experiences were used to make a better future.