No need to panic yet, when it comes to bf and AF and a return to fertility anything is possible. LOL When I was on the mini pill after DS1 I would go months
without AF, but it had come back at 8 weeks (shock, horror,gasp) and I went on the pill to control flow issues.
Have a look here
for some information that might help (and has links to other info too). It takes on average of 14 months post birth for AF to come back in ebf mums.........some get theirs back when baby stops night feeding, some get it back when they drop a certain number of feeds and some just get it back randomly with no change to routine at all. I am still waiting for AF myself, Alex had dropped night feeds for 3 weeks, then the night feeds were back (still no AF), he's on 3 meals a day now and having marginally fewer feeds, but again still no AF.........and it is possible to still get pregnant while bf and AF not returning (I know of a woman on another site who is pregnant with her TENTH baby and still tandem feeding her youngest two).
So not sure if that helps, but a pregnancy test might not be amiss if you think you could already be pregnant. It's probably just the pill at work. If you are that concerned though you could go see your Dr, but if you are happy, take a wait and see approach. I think my longest time between AF's when on the mini pill was nearly 4 months!! I did heaps of tests and they all came back negative. LOL