BC Month 2 Side Effects (pill)

I started the pill about a month and a half ago. I'm on week 2 of the 2nd pack, which I started on Monday, and my boobs have been really sore/sensitive for the last three days. Is this a normal side effect? I haven't really had side effects at all for the first month taking it, so I guess it's just throwing me off and making me nervous that I'm pregnant or something lol.