Trying to conceive

So this up coming sept I will be married for three years. I feel like sometimes my husband tries and goes for it and other times he doesn't. He said it will happen when it happens... I have not had my cycle yet this month and we only did it 4 times this months. My obgyn says in one of those whose cycle is in the middle and it's all screwy... So I'm afraid there is no hope for my dream of being a mommy come true. I will be 28 this year and would like to finally have a child. I always get my hopes up when I think I might be pregnant and then my hopes come crashing down when I find out I'm not. I am however walking and trying to eat a lot healthier to help get pregnant. I'm not the most healthy weight but with my diet and walking I have lost 20 lbs so there is hope right?