Well, I think that you are mature to now realize that it was wrong.
Here is the thing about getting jewelry: Women (almost 100% of us) are going to be excited if our man buys us jewelry. It is a very romantic gift that says..ahem...LOVE. Now, what some people may think is gold digging is actually us being excited because we feel that the grand gesture is a show of your affection, and we LOVE YOU FOR IT!
Let's say my fella said, "Heather, I'm going to put $20,000 in your account for you to spend on yourself." I would be very happy. Who wouldn't?
Now, let's say my fell took me to a jewelry store and picked out some beautiful $20,000 piece and had it customized. Well, that would make me feel very loved and I would be exhilerated and think "Wow, he really loves me!" Yeah, I would probably be a little kitten to him for a great while after that.
That doesn't make them gold diggers, necessarily. It makes them vulnerable human beings with very real emotions that you took advantage of for sex.
That being said, it was a long time ago. Say a prayer for God's forgiveness and move on. I wouldn't tell the wife, necessarily. There are some things we as wives don't want to hear. If my guy did something like that in the past, I really don't want to hear about him and other chicks.
Just my opinion.