What Could Be The Cause For Scanty And Delayed Period In A Women Having Regular Periods ?

i have regular menstruation cycle which is 28 days, my period sometimes delayed for one day or two from my expected date of period.my last period was april 17,2011 and this may i was expecting my period would be may 14,2011 but it was delayed for 9 days then i got bleeding after 9 days but it was not normal unlike to my menstruation.i only used 1 pad for 1 day and it does not full.it last for 3days same usage of pad and now in the forth day i only got spotting.am i pregnant or is this normal menstruation bleeding.i am married, 27yrs old,4 11,58kl.pls help