I'm 8W1D pregnant. Today I've had a dark brown spotting and slight cramping.

Good that you've already contacted your OB-GYN and got Heragest prescribed. Spotting in early pregnancy can happen for different reasons, some harmless and some not, so it's hard to say without a proper scan and check. Since your doctor is already on it, follow their instructions closely and go back or call them straightaway if the spotting gets heavier, the cramping gets worse, or anything feels off. Rest as much as you can and try not to stress too much while you wait for your next review. Fingers crossed everything settles down for you.

hope u & ur bb r well 💕