3 chemicals no hope

I’m 31 years old now and I have a healthy 8 year old boy. I’m struggling secondary infertility right now. My last healthy pregnancy was in 2014 and have been on birth control since and I just stop it 3 years ago. Still no pregnancy so I went to obgyn for help finally. My doctor started me on clomid for a year and a half. I got successfully pregnant one in May and another in September but I only went up to 5 days knowing and then I started bleeding. He said probably sex made me bleed. My doctor tested I’m low on progesterone so he put me on progesterone meds. He put me on folic acid meds and aspirin meds this year. I was also positive for pcos so now I’m also on Metformin. He changed my ovulation meds to Letrozole and I got successfully pregnant again but unfortunately after 8 days knowing I started bleeding again. So it’s another 3rd chemical. So traumatizing. He told me it could be another bad egg. Now he’s trying to give me a stronger blood thinner shot meds next time when I’m pregnant again. Which vitamins or supplements should I try now for my next pregnancy? Hopefully to conceive my rainbow 🌈 soon. 😭😭