So many questions!

So I lost a baby in August and then another in December, it time I tested a day or two before my missed period and had light lines. Anyways this time I tested a day before my missed period around lunch and it was positive within 10 seconds of peeing on it and the line was DARK……. Could this mean twins? (I was also on letrozole) Also , my doctor put me on progesterone twice a day and heparin shots once a day this time. Has anyone had success with that after miscarrying before?