The pill and pregnancy?!?!

So I'm on the pill and use it religiously, I had protected sex a few weeks ago ((he used a condom and didn't cum either)) for the first time. I then went on to the sugar pills last week ((the ones where you get your period)). And I got it like usual and it wasn't late or anything. I had some clots in there as well (I know sorry TMI). So does that guarentee I'm not pregnant ??? 
And what are some signs I should look out for in the future for if I'm pregnant and on the pill??
 Thank you!!!