"you are trying too hard"

I am really disappointed in those of our sex who think all you have to do to get pregnant is to sleep in the proximity of a man. That is not how it goes for some of us. I am 34, the proud mother of a 12 y/o son and 10 y/o daughter. I am trying to concieve another child. I have been trying since March '07. Not going to be as easy this time, apparently. The thing that really ruffles my feathers is hearing repeatedly "You are trying too hard. Just forget about it and it will happen." Okay, let me say this in response to that. Fooey! How, at my age and knowing that I was at least twice in my life fertile, am I supposed to not try so hard? I realize I put a lot of pressure on myself, but I am ready. I have been on PNV for 7 months and previous to that, I was on a multivitamen for 1 year. I have stopped taking all my prescription meds and I am eating healthy. I even drink my 6-8 glasses of water daily. I weigh 126 pounds, so I am not dealing with obesity issues. What is the deal here? And instead of helpful, practical advice, or simply minding their own business, I hear, "You are trying too hard."