Why isn’t getting pregnant as easy as they tell you it is when you’re young?

The frustration just keeps building and building. I try to always stay positive and look at the bright side of things, but after 3+ years TTC naturally and 2 IUIs (one resulting in a MC and the other unsuccessful period) I’m at my wits end!! I keep trying to figure out how I go from a chance of conceiving TWINS, to not even a singleton? I don’t understand. I’m in perfect reproductive health, healthier than most women in my age group, and this is still so effing hard!! My fiancé is also fine reproductively. Growing up, it was always emphasized that “it only takes ONE TIME to get pregnant”. We’re good deserving people. It frustrates me when I see all kinds of drug addicts and undeserving people with children/ pregnant. Why them and not us? I’m so unbelievably over one disappointment after the next!! When will it be OUR time? My heart breaks seeing the disappointment and sadness on the face of the man I love. It breaks my heart wondering why my body isn’t doing what it’s supposed to. It breaks my heart to continue to yearn for something that’s starting to feel intangible. Ugh!!! Who can relate???