Could i be pregnant,my period is very late and... ?

hi everyone,ok so my period has been regular since february from the pills my doctor gave me to take for 3 months but it has been coming every 18days,i have been writing it and am sure it was coming every 18days,after the 3 month pills ended my doctor gave me another one to take for a month as i still didnt conceive,then after the pill was finished i had my last period on 17th may to 21st may and thats it,4 days after my period i made an ovulation test and it was positive and i have been having everyday even before i made the test,so my last period was 2 month ago and havent had one since if i counted my period after 18 days i would be 7weeks late now,i have been having headache,backache and sore ,and yesterday i saw some brown discharge wen i wiped and today as well,just 1 time,i made a hpt last week and was neg-,my doctor will be back from holiday next week,,but am going to england then,so i wont be able to go see her for another 2 weeks,i just wanted some advice,anyone has ever tested and didnt get a positive till late,any ans will be good,thanks and i have been very moody and some smell make me sick as well,thanks and baby dust to all ttc <<,