Usually jealousy can be broken apart, as jealousy is comprised of a cluster of different emotions. Jealousy is like an onion, that has different layers that can be looked at. Some people can do that on their own, some need help (therapy sounds like it could be a good idea).
If you are able to find the time to sit and pull apart every piece of this feeling in your brain and look at each bit individually then you might not only figure out why you are jealous, but what to do about it. Sometimes the simple act of pulling it all apart and looking at it relieves the symptoms and makes a person realize that its not all bad and that really they are just needing some support in certain areas.... most of the time its about not feeling loved and needing to get to the bottom of what makes one feel loved, not getting enough time with a person, feeling inadequate in some way etc.
Hope you figure it out