12 days late

So AF is 12 days late. Never been this late except with my 2 pregnancies. Problem is I've been taking HPT every 3 days including this morning and they are all negative. I have symptoms of pregnancy, none of AF showing up. Question is...... can I use an ovulation test as a pregnancy test? A friend told me she was getting negative hpt and used the ovulation test and it was positive and she went to the doctors and they confirmed the pregnancy. My doctor won't see me unless I had a positive hpt.