Open relationships okay?

Well, most of you guys know my story by now. I've been dating my girlfriend for a little over a year now and since the beginning of september, we've been in a long distance relationship. We've been doing well seeing each other for a couple weeks every two months, and then she'll see me all summer. However, we started tossing around the idea of going to an open relationship, where we can both mess around with people and still be "together". I'm sure you all know what this type of relationship is and I was wondering if anybody has any experience with this. We're also both young (15 and 17, her being the elder) and I really don't know how I feel about this. We both sort of want to try it, but we're tentative because we are both really worried about our jealousy. We've also both expressed worries about the other developing feelings for another person. Advice please...?