There is nothing you can do to become more fertile. You either fertile or your are not. If you are not then there's a reason for it. Of course having a healthy lifestyle is always a good approach. And no stress won't affect. I was under so much stress when I was TTC that I thought it might affect but it did not one bit.
If you want just to increase your chances have sex during your fertile time (the week you are ovulating). That will do it.