This may have already been said, in which case I am backing someone up.
If you are stressed you may not be looking after yourself right, which can have an effect on your milk.
By now your body has gotten into the swing of things which can make you feel like you are drying up because you don't have masses of spare milk when you aren't actively nursing.
If you are stressed you won't be getting (as the MWs at the hospital I was in said) "broody" and in the mood which can effect let down.
Around now your LO may be gearing up for a growth spurt which can mean a LOT of time on the breast - I've done 45 minutes in every hour for three days when she was younger! It doesn't mean you don't have milk, although a lot of people do believe that.
Make sure you are getting plenty of water and extra calories (breastfeeding requires eating for two). When you are nursing look at your baby, appreciate the beautiful little thing in front of you, try to let nothing else matter for that time.
I know it sounds like one of those things that's easier said than done, but it can be done. Tink is now almost 17 months and we are still nursing! I never thought I would be able to do it for long (self esteem issues) I set targets - 6 weeks, 6 months, a year and now to see where we go from here. I am glad I have had that relationship because it has helped me with my PND and "babysitting". Being able to do something for her that we both enjoy is amazing. It will get better, honest!