False negatives, when taken after you would be more than 4 weeks along, are pretty rare- but they can happen. If your last period was June 15th, it sounds like the negative is probably accurate. Late periods and spotting can happen for a large number of reasons- pregnancy being only one of them. It could be that your hormones are a little off for other reasons, or stress, illness, etc could be causing things to be a bit odd. It won't hurt to head to the doctor and just let them know about your symptoms to see if they can give you a more accurate picture of what's happening- they can also do a blood test for pregnancy, just in case that negative is a false negative. Best of luck to you!