I'm from Germany, our system is slightly different.
Instead of a premed we have a pre-clinical part which is already part of the medical curriculum. It takes two years and in those two years we're supposed to learn everything about how the healthy body is supposed to work( the subjects are (neuro)anatomy, biochemistry and (neuro)physiology, sociology&psychology, physics, general chemistry, terminology and biology). After those two years (=4 semesters) we have our first hurdle called "Physikum", which you have to pass in order to advance to the next part. If you fail the Physikum (which basically tests everything you've learned in those 2 years) thee times, you cannot continue studying medicine in Germany. Afterwards comes the clinical part, where we have the individual specialties as subjects (internal medicine, radiology, surgery, etc.) and go on rounds, etc. This takes another 3 years (in the free time between semesters we have to do internships). Afterwards we have a so-called practical year, where you work full-time in surgery, internal medicine and a specialty of your choice for 4 months each. Then, once you're done with that, you can take your "Hammer-"exam (the word means the same in German and English ;) ) and if you pass that, you're finally an M.D. (after at least six and a half years; more if you have to repeat something).
I'm currently in my seventh semester (3 1/2 year), so I'll still have some time to decide:) That's what I always tell to myself as well, but sometimes, when you see some intern next to the verge of a breakdown, you'll wonder if you made the right choice (or in my case "will make the right choice")What year are you?
My unsolicited advice would be to choose the specialty that gives you the most satisfaction regardless of pay or residency length or strenuousness.