Three months ago I had this same thing happen. I've never in my life missed a period and for weeks and weeks I kept taking an HPT with no results. At last I figured out I was having a "Phantom Pregnany" or hormone imbalance. I've been on the pill for nearly ten years, and a lot of things can cause a hormone imbalance from the water you drink to the things you eat to the pill itself, I learned. Anyway, that hormaone imbalance eventually managed to mess with my birth control and now my husband and I are pregnant, which we're delighted and surprised, but basically just be careful if you're on birth control because it doesn't always work, especially if you have a hormone imbalance. Look into it, that's my best advice. That and get the HPT's from the dollar store, they're sensitive to 25, just as good as first response! That's the one I used when I finally found out I was pregnant, one day before the missed period.
Also stress can delay your cycle
Pregnancy tests are 99.9% accurate within seven days after your missed period. If it takes longer than that it's usually because you ovulated at the end of your cycle or that it is not a viable pregnancy and will end in miscarriage. Symptoms are NOT a good indication of pregnancy as they can be psychological, illness, PMS or even for no known reason. So don't go based on symptoms.
I would suggest waiting a few more days and test again with your first morning urine.