I was relieved that my girlfriend had a miscarriage
I don't mean to be too forward, but why?
I'm sorry, I don't want to talk about this any more
You should be supportive of your partner in this difficult time. If you are relieved, that might indicate some broader issues with your partner that need to be resolved.
I'm mad that I'm relieved and I feel like a jerk.
It is good that you recognize that your relief is wrong. You should be there for your partner in this difficult time.