Need some encouragement.

My husband and I have been together for 12 years and have been TTC for two years now. I'm 32 and he's 35 and neither of us have any children from previous relationships. I've wanted to be a mother for as long as I can remember and when I watch my niece (15 months old) I feel like that's what I'm meant to do. I'm supposed to be a mom, but it's just not happening. We haven't shared our difficulties with our families. Partly because we're ashamed and partly because we don't want anyone to know we're having a hard time. It's just that the thought of never having a baby is so overwhelmingly devastating. Not having the chance to be a mother will be my biggest regret. I'm just feeling very down about the whole thing and just need someone to talk to. Being a part of this community shows me that I'm not as alone as I feel.