Hi there
i had a similar prob and saw my physio about it (and many other preggo ailments the medical prof is making $$$ out of me atm). i too had been sleeping up on a few pillows.
he advised me if possible try to go for a lowish profile pillow, the aim is to try and get your spine into normal positioning whilst laying on your side during sleep (ie straight) usually if your head is raised too much it is not right. Anyway i already had a latex pillow which is quite flat (maybe 3 inches) but it has a lip on it which fits snuggly into my neck area. I think it is dentons brand. i have been sleeping on just that the neck is heaps better.
during day if possible try stretching neck a little by looking left to right and back again and moving head from left to right and back again whilst looking stright ahead.
i do alot of pc work and have found the stretches have helped alot.
good luck.
B