Has my conception failed me?

I started the pill a month and 3 weeks ago, everything was fine, few mood swings from pill, I had a light - moderate period from the 20th - 23rd.. A week later I started spotting brown/pink blood for 4 days, (On the 2nd of October I started taking a course of 21 antibiotic tablets due to tonsillitis) in total, this month I had spotted for 11 days on and off this month and didn't come on my period I was due for on the 22nd this month. I am slightly bloated and of course, worried! Would like to ask before consulting a GP. 
I am also very sexually active with my partner and during the course of antibiotics took extra precaution during and even for a week after from taking them. Help!? 
Thank you in advance.
Update 12/11/2015 1:18am 
Still not period as of this upload, I had tiny brown spotting yesterday morning and now 20 mins ago, slight spotting then gone.