am i choose the wrong way????

i am exhausted, i do not know whether i choose the wrong way or the right way totake my extra subjects in STPM....the extra subject is Mathematics S......first my school senior teacher....call me must take a approved from my outsider tutor and tomorrow must pass to him and i feel so stress....how could this can happen???he should tell me earliest not the last minutes days......foolish....then later i saw my ex-phyics teacher....she asked me why i take extra subject then i answer back tis is because i want to enter the public university and then the chances is very low for me if i do not take extra subjects....then she asked me other question......your SPM add maths got what gred??? then i answer i got D then she said WHAT!!! D..... i advise you mean me not to take mathematics S and is better not to take any extra subject.....i heard this answer...so harmful...my heart was so pain and broken....why i can't take.....i asked to myself....and then she told better think probably....then i said ok then later i asked her again...i got a friend also take same subject with me so he also mustdrop too then my teacher answer he take extra subjects never mind cause he is the top students in SPM.....then i just go without saying thank you....i feel like not fair....why top students can take but i'm not the top students i can't take....i already think so many times until the end of the day......what should i do.....should i just follow her advise or just continue for my taking extra subjects....i really dunno what to do....and then i told my mom about this but she just said ok and inot even advise me should i continue take or not.....i really fed up should i continue or not....i feel dizzling thinking of this....god please bless me....pls guide me what shoul i do????