how difficult is it to increase gpa?

this question is mainly to relieve my anxiety, but after freshman year of college, my gpa is a 3.278. I'm a biomedical engineering major, possibly switching into chemical engineering, and possibly going the premed route (not 100% sure yet) But I do know that I am either aiming for med school or grad school, and that requires at least a >3.5 gpa. Is it possible for me to pull this up during the duration of the next 3 years? Is it possible to get a 3.9, assuming I work as hard as possible? I'm... how difficult is it to increase gpa?
Source: Student Doctor Network - Category: Universities & Medical Training Authors: Source Type: forums