What is going on?

Stephanie

So my period is going on 3 weeks late now. I got a positive opk last Wednesday and last Friday. We bd on Friday. I have been cramping lightly on and off for the past few days and am noticing little bumps (Montgomery tubercles) on my nipples that were not there before. I took a test yesterday and today and both were negative. I have heard of these bumps being a sign of early pregnancy, but how early? Has anyone had anything like this happen before?