Thank you everyone who has posted replies, they have helped a LOT! Reading through some of the other posts on here, and having talked a bit with other people I know who are open/poly, a lot of people have recommended that I read The Ethical Slut, since it might have some more information and tips on how to get my brain and emotions to gel.
My SO and I have talked about our relationship a lot in the past couple of days, and I think we've been able to identify where the issues lie on both our parts (jealousy stemming from mistrust on my end, which stems from him not opening up emotionally on his end). We've agreed to work on our relationship before attempting to form relationships/sexual partnerships with anyone else, so that when the time comes, opening up our relationship and potentially exploring polyamory will be a happy, loving experience for everyone involved.
Again, thank you, and any further insight, tips, advice will always be welcome.