Could I Still Be Pregnant Despite A Negative Beta HCG And Missed Period?

Hi, I m taking ova care from last 1 month as prescribed by Doctor. This time when I missed my period I take urine test at home and it shows very light pink line first Time but when we tested after few hours it was little bit better then First Time. After that we consulted with Dr. and under goes beta HCG which was negative and still I havent received periods. My last period was on 16th July and I have a average 26 day cycle. Today is 30th day.. From last 2-4 days I m feeling lower back pain too. Just wanted to know whether I AM Pregnant or not.