I would set up an appointment with your Obgyn. Just because you get a negative result doesn't mean you aren't pregnant it just means that you are less likely to be pregnant. My friend was 4 months along before she got a positive result. I know that sound unbelievable, but it's true. The light headed dizzy feeling could be something else. Hopefully it is nothing serious. Try staying hydrated and check with your doctor.
You can be pregnant and not have any symptoms at all, or you could have them all, or you could have those symptoms and NOT be pregnant. Symptoms like that don't determine pregnancy since they can be symptoms of other things so don't pay attention to symptoms.
Since you're so late and got a negative result, it's unlikely you're pregnant. Many things can delay a period - stress, illness, hormone imbalance to name a few. If in a week or so you've still not had your period then you can take another test (be sure to use first morning urine when doing so) and see what it says.
Well I'm 15 weeks 2 days and haven't had any mornin sickness at all!! So just because you don't have morning sickness doesn't mean you're not pregnant. I think if you were pregnant a test would show positive by now. You should probably make a doc appt to see what's going.