I am not sure. I have many doubts.

1) Will a PhD fulfill my passion for science?
2) Will I get to make a difference in the lives of people the same way I could have made a difference by becoming a medical doctor?
3) Will I just make a wrong move by trying to get into med school. If I get accepted, will I ever succeed or will they expel me because of my mental health? (I am not from the US and we've no law against discrimination)