I had a female last year that no matter what male I put in her tub she would run laps around it for hours on end and poop-pee-urate every where.. This year she's calmed way down and is letting a male breed her..
A little blood and pee and poop is perfectly normal just means one of them is saying "Hey baby how you doing"if you think it is stressing the female out you might try a few more times but no need to force it, she might be immature or just not interested.