41 and TTC after 3 MC, but getting fed up

We first started TTC when I was 37. I got preconception counseling and was told not to worry about my age. I had a MMC at 38 and they just said these things happen. I had another MC at 39 and again they said it just bad luck. They did genetic carrier screening and that was it. I saw 2 different doctors after I turned 41 for fertility counseling and both had no advice for me. I had my 3rd MC last October and switched medical groups so I could see a highly recommended specialist.

She's very nice but her first response was "There's nothing wrong with you that I can fix because there's no cure for being old." She's convinced that the only underlying cause for my MCs is my age. I begged her to run some tests but all she did was my AMH (it's 4.12), prolactin, and anticoagulant testing. Everything is "normal", so I asked about next steps. She has reluctantly ordered a saline sonohysterogram, but still thinks I'm just too old. My insurance won't pay for the test.

I'm 9dpo today and was feeling very hopeful until noticing some spotting tonight. I always try to fool myself into believing it's implantation bleeding, which makes it more devastating when it's not.

I know everyone on here has their struggles. I just don't know why I can keep getting pregnant but always lose them. Her saying I'm too old makes me feel like it's all my fault and I've been completely irresponsible, almost a murderer. I'm totally depressed and wondering when I should give up.