First things first. What you are experiencing , these emotions, they are completely logical, even if society teaches us that it is not. Now, we, as human beings, have the ability to get detached from our own emotions, that's why we have civilization, and why it teaches you that you should feel bad over being jealous about your ex. In order to function well in it (not being called a retrograde bossy guy), you have to accept that she is free to have another sexual partner once you dumped her. In order to be a DonJuan you have to accept that girls come and go, and you don't really have ownership over any of them in our society (oh, how different it was back then); you'll be freer and they will lose value in your eyes, becoming of more value in the SM!
Now, let me explain what you are feeling so you can detach yourself from it. These girls you had an emotional connection with, they are part of your harem. You feel like they are your property, they belong to you. It's ok to feel this way, it is the way you work, as a man. You are designed by Nature to have a small number of females you copulate with, the way of Men is the way of Polygamy. The way of Women is the way of Hypergamy (I have to make a thread about this ****). So yes, your emotional reaction is completely ok. The sooner you come to terms with the inevitability of such a feeling, and about its natural nature (heh), the sooner you will be able to detach from it. To experience it as something happening in your body, in your mind, in your experience of the world, but as something you can decide to act based upon it. This is the power we have as human beings, use it well, it will make you as free as you can be.