hiya im new to this,

i have two children already and fell pregnant whislt using the coil with my second. i have calculated my period from august09 and it seems to be every 45 days. we have sex often say 3 times a week we dont use a condom until last minute purely for ejeculation. a few times hes pulled out. my last period was on 26th november 09, on day 16 after period i had brown spotting for 1 day. then on 30th december i had pink spotting for 1 day. My period was due on 9th jan and hasnt arrived. could i be pregnant? i took a test over a week ago and was negative. i have the syptoms ie weeing alot, boobs look bigger. can anyone shed any light to whats going on please. thankyou xx