Panicking

So I had a D&c done December 10 , 2014. My baby girl spontaneously stopped growing at 15 weeks Dr's have zero clue as to why. After the procedure I was bled for a day. Then 2 weeks after I was bleeding till February 14, 2015. On January 12 of 2014 I got the depo shot. On the 12 my HCG levels were back to negative from the miscarriage.

Today how ever I took a pregnancy test because I've been nauseated, frequently urinating, fatigue, and feeling scared all the time similar to the previous pregnancy. The test came out positive. And I have no clue if it's healthy for my baby and why am I pregnant while on the shot. Tomorrow I have a Dr appointment to confirm! But I'm really in a panic as to how can this be and is my baby going to be okay?