No, you're not. Not at all.
But there are three big problems: many new relationships do not work out long-term (we'll even say "a couple years"); sometimes, they end kind of badly; and if it does end, you are now stuck in medical school with that person. Probably less a problem during M3/M4 than it is preclinical years, but... I'm an M2 come August, and you're a premedder, so that's where I'm coming from.
At least for preclinical classes, I would hate to go from "oh, she's my friend" to "meet my girlfriend so-and-so" to that awkwardness of having broken up with someone you see somewhat regularly, your school's curriculum / attendance requirements (if any) depending. And then stories go around the class, or whatever other bull**** because people just tend to do that. Multiply that times ten if it's a hostile breakup. It shouldn't be like that, and ex-boyfriends/girlfriends should ideally be able to get along well -- I do with at least one of mine -- but hey, what can you do?
If you're going to **** where you eat, you gotta decide whether it's worth it to you to risk the possible fallout. For me, I've dealt with enough nonsense like that for awhile, and med school is not at all conducive to said nonsense, so I tend to lean towards the cautious side.
Oh, and yes, I have many classmates who think something similar. Not all of 'em, but still a sizable chunk.