Shrinking

I'm getting a bit pissed off now. All of my shirts shrink. They don't shrink like getting tighter, they get shorter, alot shorter. And I'm not growing. I don't dry them, I havn't dried any shirts in ages, I try stretching them when they come out of the wash, but that doesn't make a difference. They are all your cotton or poly/cotton blend. And they are good quality clothes, most of them. I can't figure out what I am doing wrong. I do wash on warm/cold. Could that really make a big difference than washing them on cold/cold? I put them on extended spin at the end too, but I"m sure that doesn't have anything to do with it. Any tips at all, I'm not fashionable so I do hate having to buy new clothes every season because the other ones have shrunk.