Pregnancy tests

Torii

So I suffered a severe miscarriage last year in May. Ever since I've had a very hard time getting pregnant. My period will be anywhere from 4-20 days late and I'll take a pregnancy test but they always come back negative. Is there anything I can do to help get pregnant or increase my chances? My doctor said it's still possible for me to get pregnant when I suffered the miscarriage. But I'm having no luck. I need help!!