(Pardon the long story... if you get bored, skip to the last couple of paragraphs for the important questions.)
Many of you know about me and ktspktsp. He is currently in PA, and I had to fly home to WA for 10 days to spend time w/my family. He couldn't come because of work (last year he was still a student, so he came home with me several times). It so happened that the one weekend we'll be apart is Memorial Day weekend, which is sad because we'd been hoping to spend more time camping before I leave for Africa on June 12th (will be gone for 2.5 months).
At one point several months ago, when I bought the tickets, I told him there was a great concert at a great venue (the Gorge), and that if he flew out for the 3-day weekend we could go camping there and see the concert. He looked into it briefly but said it was too expensive (over $300)... this also sorta bothered me since he has spent as much (or more) money on other things that he enjoys doing, without a second thought, and it seemed he just didn't want the hassle of flying out for the weekend. But that's not the main issue, and I was trying hard to not let his spending decisions get to me.
Fast-forward to last weekend. We had a wonderful night out with friends, and he was helping me (very graciously) to pack up my apartment and move out before I flew home to Seattle. He had been saying that he wished we could be together on Memorial Day weekend, and that he didn't realize until now that it was a 3-day weekend. I didn't understand that, since we had talked about it earlier, but I let it go and said I would miss him, too.
He then says that he and one of my ex-roommates (a relatively close friend) were thinking of going camping, since she would be close by and bored as well.
I tried to be fine with it for a little bit, but then I started asking if other people would be going along (he wasn't sure yet)... and he saw my red flags going up. This turned into an hours-long discussion of why it made me uncomfortable to imagine him going camping, and specifically sleeping next to and waking up with (on our inflatable mattress) another woman. I tried to express my feelings, rational and irrational; a lot of it has to do with not trusting the woman, because I've seen her make questionable decisions in the past. Part of it, I hate to admit, is that I know my bf liked her at a point before we got together. And also that I know they'll be spending more time together this summer while I am away for so long, possibly camping again.
He really felt that I wasn't trusting him, which is valid enough. I felt like my mother accusing me of things I hadn't done, or had no intention of doing. But I couldn't control my reaction; for me it just hurt because in my mind, camping and sharing a tent and mattress with someone of the opposite sex is something I've only done with him, and something that I associate with intimacy and sex with one person. I would not do that with another guy, even if my bf was fine with it... it's just one of my boundaries. He said that I'm being selfish, but that if I am really uncomfortable with it, he would tell our friend that I'm not okay with it and they wouldn't go... but that he would be irritated by being held back from doing something fun.
So I am trying really hard to be okay with this, because I don't want to be the type to "own" someone and keep him from enjoying something just because I freak out about it. I really appreciate him telling me about it beforehand, and listening to me go on and on about how I feel. I am also having a really hard time because I thought we had the same standards for this kind of thing, and now I'm starting to feel like a jealous prude and that we aren't compatible in this sense. That he'll start to resent me over the long-term. But it is how I feel... I don't know how to change it. I don't mind him doing something else with our friend during the day, but to me the line is drawn at sharing a bed (in my mind) with her when I am not there.
The other half of me wants to just let him do whatever he wants, and try to deal with it from my side of things... even if I feel really hurt, then to just try my hardest to trust him, and not assume he'll be like my past boyfriends (all of whom ended up hooking up with one of my friends after getting bored with me). I just feel so weighed down by my self, and I find myself wishing we just had our boundaries in common again so this wouldn't even be an issue.

I am not afraid of something out-of-control happening, but I am more afraid of the little things... gradual increase of intimacy, which happens when spending lots of time close together with someone in a small space and talking while falling asleep, etc etc... b/c that's what always killed my other relationships. The guy never saw it coming... he just spent more and more "innocent" time with someone else, not having sex, and after a while, our emotional connection and relationship had crumbled.
What do you guys think? I know some of you will think I am insane for being so possessive... and believe me, I see myself that way too... I just don't know how else to be, since we're both trying to be honest and communicative.
Does anyone else feel uncomfortable with the idea of their significant other going camping alone with someone of the opposite sex when you are out of town? Please be honest, either way... I need some advice and direction here.