Spotting at 6wks n 6 days

So I have been spotting for the past 2 days. On Saturday I spotted early in the morning and it was just when I wiped color brown. Didn’t spot again until Monday afternoon. That was a bit more blood colored red and brown. Called the doctor she asked if I had sex within 3 days I said yes. So she says not to worry and she’ll see my Friday for my regular appointment. I’m 39. The doctor also said that my hcg levels looked great and my progesterone levels where low. So they prescribed me 100mg of progesterone. But she said all my testing looked fine. I’m wondering if maybe anyone else is experiencing something similar. We have been trying for 5 years. Just want everything to be alright.