Negative and positive pregnancy tests

So I took two pregnancy tests. The first was negative and my friend told me I was supposed to take both so I took the other like an hour later and it was positive with a faint line. I'm confused because I have recently gotten off depo. And I'm having a positive pregnancy test and I've never had a positive test ever not even a faint line like this time. When I went to the doctor they said they got a negative test but to come back to be sure. I'm just confused. Very confused.