I'm losing it

So pregnancy hasn't happened yet for us and I'm honestly tired. I feel like a failure and I'm just at my wits end. We've tried preseed, I've lost weight, he's quit smoking, we've both started taking vitamins and changed to a healthier diet and still nothing. Our family's are constantly asking when it's going to happen and I feel like I'm letting them down too. On top of that every time I turn around someone else is pregnant and while I'm super happy for them it also hurts. I just don't know what to do anymore and I could really use a friend.