Taking another girl to the Cape

In honor of the fact that I'm going to the Cape for a few days next week (yes, I'll be posting letters from the road), here's one about a trip down Route 3.
Am I out of line in being upset that my boyfriend is spending a long weekend away on the Cape with another girl? I'd love to get some outside opinions on this. A little bit of background: we have known each other for almost 3 years, started dating very casually perhaps 2.5 years ago but have been in a monogamous relationship for 1.5 years. We don't live together but do live nearby and see each other more evenings than not (and most weekends). He is a grad student. Last fall, he befriended some seniors who I haven't met (I do know many of his grad school friends). He said he hasn't introduced me to these friends because he assumes I may find them immature (this may be true, I am in my early 30s and he is in his mid 20s). Anyway, he has apparently become quite close with one girl, whom I have never met and know very little about, except that she just graduated last month (from undergrad or grad school, I'm not sure?). She went home to Texas for the summer but is flying back here to Boston supposedly for the sole purpose of going to the Cape with my boyfriend (although I could probably assume she will visit with other friends while she is here). His parents own a house on the Cape, and we recently spent Memorial Day weekend there together (with his parents) and had a wonderful time. I have told him I am very upset about this and that I think it is inappropriate, but he insists that I am being ridiculous, they are simply good friends. A few weeks ago I said I would just get over it and stop being jealous about this. I should note that we do not have any history of cheating between us, and that I am normally not jealous of his female friends. Yesterday he told me this "weekend" has now turned into leaving on Thursday night and coming back Monday night (4 days!). He says they will be "chaperoned" since his aunt and uncle will also be at the house for the weekend, and that I have nothing to worry about since he loves and cares about me. He is actually quite angry and offended because he believes that I don't trust him. He can not understand why this bothers me, he thinks it’s the same as when one of my best girlfriends and I (who I have known for over 15 years) go to my parents in Vermont or take other trips together. My issue is not that I assume he is going to cheat on me with her (I do trust him), it’s that... 1) I can't understand how two people (guy & girl) can spend 4 days straight together in a 1 on 1 situation and not be either romantically involved or long-time friends (i.e. if this was some friend from high school or college that he has known for years, or traveled with in the past, I might understand). Is this girl interested in him? Can he blame me for wondering? 2) This whole thing would be so much easier to swallow if there were a group of friends going. 3) I find it almost embarrassing! How do I tell people who might ask, "Where is your boyfriend this weekend?" and I answer with "Oh, you know, he just went down to the Cape on a 4-day vacation with some girl I've never met and that he's known for less than a year" 4) Not only that, I can't imagine what his parents/family might think? I have spent a fair amount of time with his family in recent months - how might they react to the fact that he brings a different girl to the Cape house each month, even though I have been the one present at family gatherings for the past year or more? Please tell me why I should either calm down and forget about this (I admit I have some insecurities, don't we all?), or that I am justified in my reaction - I lost a lot of sleep last night over this! THANK YOU for your help. Trying not to be Jealous, Watertown, MA

A: TNTBJ, Ok. I'm going to start with your numbered points (and thank you for being so organized). 1. Heterosexual men and women can absolutely spend time together platonically, even on vacation, even if they’re new in each other’s lives. It’s totally possible. But ... 2. You’re right – it would be easier to swallow if there were other people going on this trip. He should be sensitive to that. I’m with you. 3. Don’t worry about embarrassment. The only person who really cares about this is you. 4. See point 3. His parents might get confused, but is that really the problem here? Let’s be honest. You’re afraid he’s going to cheat or that he’s lining her up. You don’t understand why he wants so much alone time with a person who just happens to be a college gal who has time to run off to the beach with your significant other. The fact that you feel this way doesn’t mean you’re clingy or paranoid. It means you’re normal. Anyone who says they wouldn’t feel the same way is a big, big liar. Yes, this would be easier to understand if they were longtime friends who met in grade school. It would also be easier if he introduced you to her – if he made this new relationship less threatening in any way. And what’s this nonsense about a chaperone? Does he need one? My guess is that he’s a guy caught between his 20s and 30s. He's not quite ready to leave the kiddie table, which is why he found a group of college seniors to validate his wants and needs. Meanwhile, you're at the grown-up table with rules, timelines, and real commitments. If he can’t join you in the land of adults – and if he won't introduce you to these friends and show them (and you) that you’re a real part of his life – you have every right to assume he’s leaving you out for a reason. He should know better. And he should care about making you feel safe. You’re not wrong. And you can send him a link to this if you need to. I’ve got your back. Readers? Do you agree? I’m all for platonic trips to the Cape, but this one’s sort of not so great. Thoughts? Share here. No sleep 'till Dennis, Meredith