i graduated med school in 1993 and have been a family physician for 20 years.
when i was growing up my mom worked as a nurse in labor & delivery. she worked alongside the obstetricians when they did c-sections and she would always tell me that i had the hands of a surgeon.
but i don't think that ever really influenced me. what did influence me was tagging along with her at the hospitals. i realized early that what i didn't want to be was a nurse - because they work really hard.
i can't say that anyone ever directly told me that i didn't have what it takes to be a doctor. but i did have some similarly discouraging experiences. every single doctor that i spoke with about my intentions discouraged me from going into medicine. but that was always because they were pessimistic about the future of medicine.
i did a lot of pondering on that. was medicine truly that bad of a career choice? or was it maybe some ploy to find out if i was truly committed to going into medicine?
later, when i was interviewing at medical schools i found it odd that every single interviewer made a point to ask me if i had made any plans in case i didn't get admitted. again, it left me wondering if this was another "test" of my resolve.
so if you do choose this path you should be aware that negativity is the rule, not the exception.
let's get back to your situation.
my guess is that your demeanor doesn't seem "doctorly" to some.
what you'll find is that every specialty in medicine has its own personality. for example, athletic types tend to be drawn to orthopedics, brusk types to interventional cardiology, flaky types to psychiatry, etc, etc.
of course, those are stereotypes and definitely don't apply to everyone. but i'm telling you this because i've found that just about every personality type is represented in medicine just like in the real world. there is no single "doctorly" demeanor. it's simply a stereotype. a myth.
of course, there is the possibility that perhaps you were belittled because of poor academic performance. now that would be much more serious and i don't have anything positive to cheer you up if that's the case. medicine is undoubtedly very rigorous academically. and i don't see that ever changing.
it sounds like you have some motivation. next you need education. later you'll need training.
what have you researched about medical education and medical careers? have you spoken with doctors or other medical professionals? spoken with your school counselor?
enthusiasm is a good start. but you need to formulate a plan. what will it take for you to get from point A to point B? is it practical? is it even possible? what's it gonna take?
so if you're truly committed then don't let critics stop you. but be realistic about the struggle. make a plan.