I had my period early from the 1st in the morning to the 3rd mid-day *I was supposed to start the 5th* (as usual my only last three days) but two days later (when I was supposed to start) I had spotting and don't know why, I mean if it was the day after I finished I would understand but it was two days later. Why did it happen?

That's difficult to answer over the Internet. Chances are since you already have short menstration, your hormones were still low so spotting occurred. Its not unusual.

I wouldn't worry too much about it.

Sometimes you think you've finished then a few days later restart... that happens sometimes... don't worry, lots of women do

Sometimes you think you've finished then a few days later restart...that happens sometimes...don't worry, lots of women do
But my periods always only last three day well actually usually I'm completely done by the fourth day but this time it was a little shorter and usually never ever have spotting I think this is the second time it's happened to me I'm sure it's probably nothing but I was worried because around the time I was ovulating I had unprotected sex about three or four times.. . But it should be OK because I had my period right?

There are no guarantees.. but I would say I would think so.

I think you have to wait a while before a pregnancy test would work, but to set your mind at ease I would do one as soon as possible, purly for peace of mind.
I'm sure you'll be fine though so try not to worry.