Our feelings are very often unfair. That doesn't make us horrible people, it just makes us human. Something that most of us are able to wrap our head around, but which is harder to internalise. Your feelings do not make you a bad person. You can't change your feelings by wishing you didn't have them, it is not that simple. Your feelings may change with work and time, if that is something you choose to pursue.
First thing I would say is that it's good you are thinking about these things even in this situation where you don't have to
. Good for you. Second thing, the key to negative feelings is not to stop feeling them, but to focus on the fact that they are just feelings and to let them pass.
It is so simple and yet so very very difficult. But managing feelings is all about that, not letting ourselves be guided blindly by them (because they are just feelings), and to learn we will be okay even if we are feeling, at that moment, like crap.
I'd like to recommend http://www.morethantwo.com/
for good stuff about jealousy&poly. Good luck with everything!