tough decisions

Currently on the verge of making some tough decisions in life and i'm only 17.
My mind is in this utter state of confusion and turmoil.I have no idea about what i should choose over what and why I should do so. This hopeless situation is taking most of my precious time which i would have rather used to just sit and stare at nothing in particular, listen to those tiny noises which you would only observe if u weren't as preoccupied. In short , now instead of just idling my time im actually reduced to think about my future. And my 17 yr old slightly immature mind may make a decision I might regret for the rest of my life!
My choices are really simple straight forward choose between two streams. One of which I have no idea about and whether I would be good at it ie commerce and the other being a subject specifically biology (dentistry) which i've been comfortable all my life. Seems simple I probably would have gone with choice two , I really would have. But we're talking about dentistry here. I can never imagine myself sticking my hand into somebodies mouth (ugh!). Kinda grossed out by that fact but still its an option. Close family flooding me with opinions, do commerce! do commerce! while my dad is of the opinion that i should play to my strengths and hes all for dentistry. Great career options in the future he says. Of course both have great career options. It depends on the person and the way he can cope up with the different stress levels which comes with the job description and of course talent and a natural flair for it.
After weighing the pro's and cons for both over and over again, talking to people wondering about whether what im doing is the right thing.... im still back to where I started . I'm still confused. Its just me, i'm always indecisive, hesitate till the last minute, and of course overly cautious.Just have to think about it . And since I have a lot of free time and I can sacrifice some days of idling sigh I'll have to sit and think it through. After all , my career and the next 50 years are at stake ( sorry for the melodrama, its just me). But as they say kesara sara- whatever will be will be.
Any suggestions are welcome, feel free.