When I was 17 years old, I was flying by myself from LHR-BRU-FLR (I think I flew in on BMI, but I can't recall what airline I was flying out of BRU on, but I had to go through customs because I was flying out of another Terminal or something like that) - I had 2 feet long hair & a full beard at the time & had been traveling for about 2 weeks already, living out of a backpack & probably hadn't done my laundry or anything yet. I got stopped by customs for being suspected of having a fake passport & got pulled into a questioning room for about 2 hours & they went through all my stuff before they realized that I wasn't a threat. Haven't flown back in/out of BRU since then...I doubt you'll have too many problems now & as long as you look & act respectable, you shouldn't have any problems - it's not like you're staying in the country too long...

That said, the only other time I've gotten the third degree was at ORD after the customs agent asked me how long I had had been in AMS & I told him about 26 hours. He asked why we went for such a short time & my friend who was traveling with me held up a box of this really good strawberry shortcake he got at a bakery for his sister & said "They've got the best shortcake in the world!" The customs people x-rayed the short cake & let us go through (after explaining that we were on a mileage run & were from DC & still had to catch a flight to MSP & then on home to IAD).