It sounds more like an ovarian cyst, if it is too early to test for pregnancy. Ectopics typically don't hurt in the first couple of weeks after ovulation, since the first six days they aren't even implanted (they are still in a shell and can't implant until day 5 or 6 after ovulation). Ovarian cysts can hurt pretty much any time after they form, which would be a few days after ovulation.
Wait until your period is due, and if the pain gets worse go see your doc.
I agree that it would be too early for pregnancy unless last month you actually had spotting and not a period (happened to me). I have also had an ovarian cyst. They are painful. Most are harmless though and pass on their own (feels like a painful, heavy period). Since we don't exactly know, I'd consider seeing your doctor if this keeps up. Your ob/gyn could determine the situation very easily and pregnancy tests at home are cheap and an easy thing to do for info anyway.