When is a girl most fertile? like when would i be most likely to get pregnant?

Mid-cycle days 10-18: If you have regular monthly periods, days 10 - 18 are the most fertile time and you can have sex every other night if ttc. If trying to avoid pregnancy, 'fertile days' is not a good method. If you are regular, you can also use an ovulation predictor test and have sex for the three days starting with a positive test. If you have irregular cycles using the ovulation predictor kit is not a good idea.