Tired of trying and failing

I've been with my husband for 5 years married for 2 and trying to convince for 3 years and had no luck but I want nothing more than to be a mother and he wants to be a father and I know this because it was actually his idea to start trying and every time I walk past a baby or even the baby section in a store I feel extremely sad and like I'm falling at my duty as a wife and as a women am I crazy for feeling this way or is it normal