Late period, negative HPT's, is it too soon to blood test?

Hi everyone. Well I am still not getting my period. My period was due Mar 6. I am like clockwork on a regular 28 day cycle. I am having all the symptoms that I had with my prior 5 pregnancies (5 pregnancies, 3 births). However, the only thing different this time is that my pee tests are coming out negative. With my other pregs they were positive sooner. I am going in for a blood test today and I want to be sure that I do not have a cyst, an ectopic pregnancy, or an infection. So what do you guys think? Could I still be pregnant and get a positive blood test today with two negative HPT's? The last neg HPT was Tuesday and it was on a EPT so I didn't think I was preggo. What are your thoughts?