Wondering if my mindset can influence getting pregnant!

I did go to a gynecologist and she told me everything is fine with me but cuzof me being veryyyy light ( 45kgs ) I always think that my body wont let me get pregnant.. is there a chance that my thinking could actually do that?

I did try gaining weight in a couple of ways but everytime the doctors would say im as healthy as a person can get. They ( went to multiple doctors ) told me age and pregnancy are the only two things that will influence my weight gain.