Negative test but two days late with period.

My boobs have been hurting for nearly two weeks now. The last four days they've became more sensitive. My nipples are now pretty sensitive too. Nothing can rub on them. I haven't worn a bra for two days because it's uncomfortable. My boyfriend has noticed they've changed in size and feel more firm. I was suppose to start my period yesterday and didn't. I took a pregnancy test and it was negative. Im on what would have been the second day of my period and still have not started. My boyfriend and I have been trying to get pregnant and this is happy news for us, I'm just thrown off by the negative test yet no period. Can any one offer some advice please?