As your cervix begins to dilate, there are tiny blood vessels in it that may burst and bleed a little, that's the "bloody show" that some women experience. It's perfectly normal, especially in the small amounts that you're describing.
It can mean that labor is just around the corner, or it could mean that you're dilating very slowly and by the time "real" labor kicks in, you'll already be at a 5 and it'll go fast!
If it's amniotic fluid, it will *typically* pool if you lay down, then when you get up, you'll notice increased leakage. So go lay down for an hour (do some kick counts, read a book, take a nap) then when you get up pay attention to see if you have any leakage.
Amniotic fluid is typically clear and odorless. As opposed to urine which will be somewhat colored and have a scent. Discharge will be milky-white, stringy, or blood-tinged.