I changed my 3rd gynae too when I was at close to 6mths...
If you are not comfortable/unhappy with the gynae, then do what is best for you.
I switched my 1st gynae not because i was not happy with him (infact he is a nice and patient dr) but his fees are too ex. 2nd one found her too commercialised.
Go with your heart. After all, it's you who are pregnant, so you have the right to choose !!