SO SCARED NEED HELPP??10 points?

ok so about a month ago i found out i had BV, i was too embarred to go to a doctor, and plus i thought al they were going to do was give me a perscription for flagyl, because it treats what i have..so i ordered the flagyl 200mg online and i just got it yesterday, now im too scared to take it because ive been reading all these reviews and they're all BAD! whats the difference between the 200mg and the 400mg or 500mg, do you think its safe that im using 200mg rather than the stronger ones?