should I have another baby.

Okay, that's fine, but propagating myths about breast feeding as the natural way of contraception isn't something a "medical doctor" should preach. He should know better.
Women can become pregnant despite that.

So if this medical doctor can make such a stupid mistake that a first year medical student would laugh at, how can he be reliable with regards to religion?

Re: should I have another baby.

okay since we r on the topic of children and contraception i will add another question
is it permissable in Islam to end a pregnancy due to severe complications and health risks to the fetus and mother due to the mother being on medication?