If you have been checked and the doctor has done a physical exam then you would do best to follow the doctor as we are not examining physically. Time the contractions and if they are regular and come closer to each other then report to the doctor again.

there is something called Braxton Hicks which is false labour. whenever u get contraction try timing it. n if it's not regular then u don't need to worry. just listen to ur doctor I would suggest.

but she said contraction is due to vaginal infection

If your cervix is one finger dilated and you are having regular contractions then yes all signs indicate that you are in labor. Please do have yourself checked by the doctor asap as it is a little early and baby should be in the womb till about week 37.