Period and TTC after miscarriage?

So I had my miscarriage on March 6th right before my 6th week. I bled for 3 days. I know it’s only been 3 weeks and the doctor said 4-6 weeks, but did anyone get theirs earlier? Also, does anyone know when you’re most/least fertile after a miscarriage?

Husband and I are planning on trying after my next cycle so we’ve been careful... buuuuut last night we got a little carried away and were not careful. How likely is it that one night would get me pregnant?