Anybody get pregnant while bfing without having period?

I think this may be happening to me right now but I'm not sure. My son is 15 months old and still bfing 3-4 times a day. We use protection (condoms) but last week it broke. I felt pregnant super early last time, he is our third baby.. so I was only 3.5 weeks when I started having low cramping a little bit, lots of gas... etc.. Now, I think I might be but got a bfn this morning and wondering if it's too early. Or, are these same symptoms maybe just my period finally gearing up to arrive?? I have never gotten pregnant before while bfing, so I don't know if anybody thinks this may be the case here or what? I feel a little nervous about the whole situation. We weren't planning this but if it happens we'll be happy, just a little unprepared! I can't get it out of my head since this is the exact way I felt in the beginning with our little guy. I need to get off the computer for a couple days probably and test again Monday!