Thanks for the query.
The dry and darker blood may indicating collected blood in the uterus during menstruation
As your cycles are regular, no need to worry.
You consult gynecologist once, get examined and go for ultrasound
Then with her advice you can go for follicular study
to track the ovulation.
Then plan unprotected intercourse
around that period.
This will increase the possibility of pregnancy.
For more details you can ask me directly through the premium forum.