spotting before my period...

Hello I’m 33 years of age and my husband and I are trying for a baby. My last period started on 06.06.2011 and finished on 12.06.2011 on a 30 day cycle I am usually between 30 and 32 days. So I calculated my ovulation dates and we had sex on the 14 June (9th day of cycle) and then 22 June (17th day of cycle) which by all accounts I may have straddled it and completely missed my ovulation dates. On the 26 June (21st day of my cycle) I noticed some spotting pink colouring in my discharge, I presumed it to be an early period as I have had 2 periods in my menstrual cycle twice before in my life time. But by the 2nd day there was none, then it began again. Basically I had spotting on or off for week and now I appear to be on my period from yesterday 04 July so on a 29 day cycle. At first I thought this may have been implantation bleeding but since I can now say I am on my period I’m just curious whether this spotting maybe an indicator of something else. Also I just see it to be extremely difficult to work out my ovulation dates so we’re likely to attempt at having sex every 3rd night to give us the best fighting chance possible