urine leak, how ???? 30 weeks

when 27 week, i noticed always wet underwear, i made urgent appoinment saw OB, scan showed normal it is not leak from vagina, he asked me if it is urine leakage, i answered NO, if urine leakage , i can feel it, but after few day abservation, i think 80% is urine leak, i also dont know to differentiate whether is urine or not, now must wear pad in order to go out of house, how??? pls help me, if any experienced sister have the same problem.....plenty of thanks....... by the way, first baby, i am 29 yrs old