And therein lies the problem.
You underexposed.
A lot.
If you had your meter set at EI 640, and you metered incorrectly away from the camera lens toward the main light in the background, you probably shot the film at EI 3200, or 3 stops underexposed.
I will bet you that if you do the Sunny 16 test that I recommended, you will find that your film will process just fine at Dilution H, at the processing time you gave it.
If you can't hand hold it, you have to use a tripod.
Or accept blurry pictures.
But you have to get enough light onto the film.