<human>: I didn't know whom else to talk to. Reddit seems like a good place to throw this problem out there. I could use some advice.

I started "casually" dating a girl a couple weeks ago. We've been out on several dates. She has a very packed work schedule so I haven't been trying anything at the conclusion of the date; she always seems fairly burned out after a day of work. We've kissed and such, but nothing more than that. I recognize that she's making an effort to see me, but I haven't tried anything intimate because I assume she wants to rack out early for work the next morning.

She and I both understand that we are "casually dating", however I don't think that we have the same definition of what that is. For me, casually dating really means I want to date, but I'm not making any commitments regarding where it's going. I reserve the right to end it without any hard feelings if things just aren't working out. It really is a trivial definition, because this is essentially every early-relationship date ever. I only ever feel comfortable dating one girl at a time. I may have several first dates scheduled, but if we go on a second, that girl is the only one.

Anyways, I'm pretty sure that she is seeing another guy on the side and slept with him last Tuesday. Maybe he's way smoother than I am, or unbeknownst to me she's been seeing him longer...no idea.

We've both been having a great time during dates and enjoy each other's company, but a couple of weeks ago she proposed a trip over the upcoming long weekend. We're supposed to go white water rafting, camping, and bungee jumping; it should be a great time. I'm having more and more trouble getting over the fact that she had sex with some other guy this past week though.

Should I cancel the trip?
or
Tell my scumbag brain to stop messing with a good thing; that she was in fact within the understood bounds of our current relationship and didn't do anything wrong?

Just putting this to paper has been very therapeutic, but I'm looking for your advice Reddit.

Provide a brief overview of the text.
<bot>: Casually dating a girl who I'm sure recently slept with someone else. We have a fairly big trip planned this weekend and I want your opinion as to whether or not I should be pissed off.