False positive?

So I am 40 days late. When I was 5 days late I took 2 pregnancy test and both were negative. I took 2 more when I was 17 days late and again both negative. I just figured my diabetes and pcos were causing a missed period. I still had one test left (digital equate test) and took that yesterday. It was positive. I went out and got another test today (urine) and it was negative. Has this happened to anyone else with a digital test? I do have an appointment with the dr next week.