Has your AF gone a bit screwy since you started TTC?!

I've just had a period that lasted three days and was just light spotting on the third day. The prevous month it lasted 4 days. I normally have very heavy periods that last 5 days. I started TTC at the end of April. I've never been on the pill.
Is this a common thing? Are any of you experiencing the same thing? My periods are normally very reliable and they normally last the same amount of days - like clockwork! This month my period was just brown old blood at first and then it normalised but dried up at the start of the 3rd day.
What do you think guys?
S