Paranoid?

I had a baby 8 months ago. Been on the pill for around 3 months and my periods were all over the place. I think that's due to me being forgetful at taking it every day. Well I'm on the pill which has to be taken with 3 hours on the same time everyday. 
The last 6 weeks have seemed to get a lot better. Had a normal 5 day period 3 weeks ago then 5 days after it finished, I had a day of a brown like period. It only lasted a day. 
I'm super paranoid I'm pregnant again!? Is this a symptom?