Trying again after loss!

Melissa • I`ve had 3 preg I lost the first then had my rainbow baby then I lost my son this year trying for baby 4(1 living child)
I've had three pregnancies I lost my first one then became pregnant with my daughter for months later she is now 4 1/2 and then I can see if my son last year and lost him this year at 17 weeks pregnant i'm finally rates start trying again does anybody have any advice? I'm already taking prenatal vitamins baby aspirin and full of acid as prescribed by my doctor.