Stressing the F out

So I’m 3 days late and I took a test on the first day of my missed period and got a faint positive waited till the next morning and got a darker positive I went in yesterday to get blood work and my OB called today and asked if I was bleeding which I haven’t been and she said the levels were low and maybe I’m earlier than I think and to go back today for more blood work....... I had a miscarriage in June so now I’m really freaking out. Has this happened to anyone and everything be okay?!