18 weeks pregnant

question lang po . about s bilang kung ilang weeks na ba aq preggy . . last mins . ko is dec 19 first day . then ng Pt ako bay january 5 kasi ngpa papsmear ako. ng negative sya . then medjo di ako comportable s feeling january 19 ng pt ako 2 times and its postive . san ba aq dpat mgsimula mgbilang . . sa may further idea lang .. thanks in advnce ..