1 Day Period. What's going on?

My cycles are 28 days, they last from 3-5 days every month. 

Me and my SO use the withdrawal method (pull out method), been using it for going in 3 years. 

Last period was Oct 9, had sex on Oct  22 (forgot I was ovulating!) Hubby did pull out. 

CD 24 I had a couple drops of blood on my panties. (We hadn't had sex in 3 days so it wasn't from sex.) I thought right away it was implantation bleeding. I was scared out of my mind! I could do nothing but wait, so I waited for AF to appear. I was supposed to start Nov 6, but nothing. I had brown discharge on Nov 7 (day after AF was to appear) then later that day pink spotting. Put on a pad and nothing the first few hours. Later that day I started bleeding normal flow. But then today Nov 8, I stopped mid afternoon. Nothing on my pad or toilet tissue. 

My question is, is there a possibility I could be pregnant? 

And if so, when should I test? 

Are there any other causes for having a 1-2 day period? 

I have a 3 year old so it wouldnt be our first baby. 

Any answers, advice, or opinions are welcomed. Thanks a bunch!