Don't contact the ex. That will only lead to bad things. Talk it out with your wife. See if you need couples or sex counselling. It's okay to have a problem like this. But you have to work on it if you want the best results. Compromise is needed on both ends, and if it can't be had, you two may not be compatible in the long run. Sex is one of those things that if you two can't compromise on it, you'll both just end up resenting the hell out of each other and one or the other will cheat to get what they want. It's one of those things that can end a relationship.
Thanks for all the responses everyone. I will take this advice to heart and not contact my ex. I really love my wife and I want to work out these sexual frustrations with her. For those who asked what I was into with my ex. We did a lot of a**l play, sex in dangerous places(like in the movies or in her grandma's pool) and sex slave roleplaying. I tried suggesting those things to my wife but she just wants to keep doing what we do all the time which is sex in the missionary position. So you can see why I still fantasize about my ex. I will however try mentioning sex therapy and see if that can work. If you still have any advice about this situation or wanna add something more I will greatly appreciated it. Thanks again.
I think talking about why she wants to keep on as you are might be helpful. Caveat: the reason might be that she's a vanilla lady who genuinely likes things as they are, and has not gotten her kicks from other things she has tried in the past. There is not necessarily going to be a lot of room to compromise, and if that's the case, please be sure to hit the "can we try this" brakes when she says no. You don't want to be That Guy. Sometimes, though, people are open to more kink in theory, but don't know about the kink in question, or have insecurities, or had a bad experience with said kink, or haven't had a lot of exposure to said kink. This is the kind of thing that conversations-- again, with a couples' or sex therapist if you feel it would be beneficial-- can open up. Talking it through can help people understand and clarify their positions (haw haw) on a given act. Talking it through can introduce people to new ideas, which may or may not seep into their head and change their thinking.
To remove it from such an emotional context, I was not sure about having a dog someday, but my boyfriend is a dog person (and cat person, and rabbit person, and reptile person). It was important to him. We haven't been able to have dogs in our rentals, but now I am open to the idea provided we have certain boundaries for the sake of our furniture and our cat. In that situation, it was a matter of me never having contemplated it and having been around some spectacularly irritating dogs in my life. Given time and no pressure, I got to think it over and realize that hey, they're animals and I still like them, and we can set rules. The value of letting me think it over without pressure is that I had time and I didn't feel like I had to come to a certain answer. That approach, adapted for therapy should you choose it, is the best way in my experience, because you're not guilt-tripping each other or obsessing about this one issue in an otherwise awesome life.
I recommend The Pervocracy. It's a kink-enthusiastic blog, so there's a lot of how-to on broadening your sexual horizons, but it also discusses compromise and communication. There are a lot of entries about having difficult conversations or setting limits you both can live with. Plus the author makes fun of Cosmo every month, and that's hilarious.