I've had to change meds several times, and mostly because one is very expensive/doesn't work/side effects are bad.
I have not had major reactions switching from one to another. If you are on a higher dose of a med, then you should talk to your Dr. about weaning from one and starting another med.
Lamictal is a very expensive med, and I did not have insurance when I was taking it for about 2 years and mostly paid for it out of pocket, or got samples when I could. So I am sorry that your insurance wont cover it.
There are a few other meds that also work as mood stabilizers, so don't despair.
"What is life? An illusion, a shadow, a story,
And the greatest good is little enough:
for all life is a dream, and dreams themselves are only dreams."
~ Pedro Calderon de la Barca, Life is a Dream