I used one through my 2nd and third tri..........an absolute godsend! I got mine, and its pillow case, from Spotlight.

This may be TMI, but I noticed that my discharge levels were high in the third tri, plus my boobs were leaking, so I needed to wash the pillow case quite often (paranoid about smelliness!) as I had a habit of wrapping my legs round one end of the pillow and had the top end tucked round my boobs.