Pregnant one month after a miscarriage?

I had a miscarriage on June 22-23, I went to the doctor and she did a sonogram and didnt see anything, I was less than one month pregnant, they did a blood test and they said my levels were really low for hcg. They said I can try again once I get my period. So I was supposed to get my period around the 21st, but didnt I didnt think much of it b/c I know my cycle would be different, I have been getting some light spotting here and there and have sore which I didnt get last month. Also last month, when I took the pregnancy tests the line that indicates ur preggers was very very light. Yesterday I took a test because I was planning to book a flight for two weeks, so I just wanted to make sure it was negative, but imagine my surprise it was positive!! The both lines were dark blue and came up seconds after I took it!! Is this possible that I am preggers? I am scheduled for a blood test to confirm, but I just wanted to see if anyone had this happen to them? I just dont want to get my hopes up, would it be possible the levels are still in my blood from last month even though it was really low?