Wacky periods 😣

We've been TTC for 6 months and I know it can take a long time, but I'm really just starting to lose hope. My periods are extremely odd I normally have around a 40 day cycle. I've gone to my OBGYN and he's offered bc to help control it but I want to have a baby so obviously I'm not going to take bc and there's nothing wrong to effect my fertility he said. I've spent so much money on ovulation tests and pregnancy tests and I just feel like I'm failing my husband each month 😞😞 does anyone else have odd periods and successfully conceived ? I'm ready to give up. I already have three step daughters from his previous marriage but I want one of our own so bad !