Frustrated

Idk what Im doing here, Im so lost... I have so many issues that I don't even know where to begin.
So, I'm 28, my bf is 37. In April 2009 is our 10 year anniversary. We've been trying for a child for so long. We have never used protection,and I have yet to get pregnant. :o( I am just to the point that I am so overwhelming saddened. My cycle has been irregular since my very 1st one.
He has 2 children from a previous relationship, which over the years I have done more then my fair share of raising, and I am just waiting patiently for my turn. It seems that every time I turn around, I'm seeing more and more presious baby bumps, and due any day bellies. I feel like such an awful person to say that I am so jealous of all the expecting moms' I see daily. Not to mention the babies!!! They're every where! I feel like if I can't get pregnant that I so much less of a woman then all of you! Almost as if I have no purpose. As long as I can remember I have longed for pregnancy. I remember being 10 years old playing house walking around with a pillow under my dress, ready to be a mom! LOL! But seriously, I some times wonder if I haven't been blessed yet because I'm a bad person?? I have done things in my life that I regret, sure, who hasn't right? But I really wonder if I have truely hurt someone so bad to the point that this blessing was taken away from me? Just took another Negitive hpt today! :o( Any thoughts? Maybe just a couple of heart felt words of encouragement? Baby dust? Any thing?