Its definately not you thats thick lol, its your paint, and the texture your getting I expect is a lumpy effect.
your lines will dry in, but will leave a slight ridge, sometimes this is caused by the actual roller, and its mainly from the end of the roller sleeve just slightly jutting out from the arm.
Try and bang the actual sleeve so that is fits snug on the arm.
if your ceiling is flat and you want a flat finish, then a short pile is okay, as it sorts of floats across the ceiling, and is very smooth.
You need to sand the lines/ridges, and start again.
Add some water and mix well, get your stick, and if the paint blobs off the end, then its too thick for you, try to get the paint to run off, but not like water lol, more like a thick runny double cream
Try adding about 10%-15% water for the first coat, and if you find its too thin, then for your next coat add less water.
You will be able to tell after the first couple of rolls, as you will notice how the paint goes on
Then all you have to do is to add either more water or paint.
If you still find you get lines/ridges, as I get them the odd time on ceilings,(funny enough I never get them on walls) what I do is, carry on rolling the area, and just before I am due to load up the roller again,(as now your roller has no paint on it) I then go over these ridges very lightly and roll them out, then I load my roller and go on to the next bit.