TTC Help me

Courtney
Can someone help me? Me and my husband have been trying for about 5 years to get pregnant. We got pregnant with twins but we lost them a year ago. We just gave them names. My question is.... Why is it so hard to conceive? I'm extremely fertile. We have sex often. Especially at my ovulation times. And especially at my highest fertile days. Why can't we get pregnant? I don't have long. My husband was told he only has 8 months to live. I want to get pregnant so I'll always have a part of him with me. Please help. :'(