My cycle has been messed up after misscarraige?

I had a miscarraige at 9 weeks back in July, I have had 3 cycles since. Long months, no ovulation. We are still Trying to conceive but it's not happening obv I am 39 and it would be our 3rd child. I've always had a 28 day clockwork cycle and always new when I ovulated, Why has it messed me up so much?