Each person must act according to his level of bitachon. Although the Ramban says, that a true yorei Hashem (dont remember the exact words) doesent go to a doctor, the Steipler shouted at a baal bitachon for not going to a doctor, insisting he must go.
R. Y. Berkowitz, in his new book “the 6 constant Mitzvos” makes the point that we don’t work on bitachon. Rather we work on coming closer to Hashem. Bitachon is a natural outgrowth of being close to Hashem… To skip the coming closer to Hashem part will not make our bitachon stronger.
A huge huge baal bitachon should probably not purchase