Your experience (of feeling like Olive has given up on you) is unfortunate. Should never feel like that...and I hope you have success soon.
In terms of evidence for heparin, this is from UptoDate....(a clinical resource used by HC providers)...
INEFFECTIVE OR UNPROVEN THERAPIES — The following therapies are not supported by data and we do not recommend them.
Aspirin with or without heparin — A large randomized trial found that neither aspirin nor aspirin plus heparin improved the live-birth rate of women with unexplained RPL . In this trial, 364 women with unexplained RPL after a thorough evaluation were randomly assigned to receive daily aspirin (80 mg), aspirin plus nadroparin (2850 international units), or placebo. Aspirin or placebo was begun preconceptionally and nadroparin was started as soon as a viable pregnancy was documented by ultrasound. Among the 299 women who became pregnant, the live-birth rates for combination therapy, aspirin alone, and placebo were not significantly different: 69, 62, and 67 percent, respectively.
Similarly, another trial randomly assigned 294 women with ≥2 consecutive unexplained pregnancy losses at ≤24 weeks to treatment with enoxaparin and low dose aspirin or no treatment; both groups received intensive pregnancy surveillance . Medical therapy did not reduce the rate of pregnancy loss, which was 22 percent with drug treatment and 20 percent without it.
Low-molecular weight heparin — Low-molecular weight heparin (LMWH) is frequently offered to women with unexplained recurrent miscarriage. However, trials show no benefit to LMWH treatment in women without an inherited thrombophilia [49-51]. One double-blind trial randomly assigned 258 pregnant women who had a history of unexplained RPL (two or more consecutive miscarriages before 15 weeks gestation) and a negative thrombophilia work-up to either subcutaneous daily LMWH (enoxaparin 40 mg) or placebo . Enoxaparin treatment did not improve the chance of a live birth. In another trial of 449 women with RPL and no thrombophilia, there were no differences in live birth rates between women randomly assigned to dalteparin 5000 IU daily versus placebo (86 and 87 percent) .