Why does it hurt so bad?

It's been a while since I worked out, actually the whole summer, so I thought, today's the day!! I've thought this the past several Monday's but today really was the day and since I couldn't be bothered to go all the way to the gym, I thought a leisurely jog around the neighborhood would be good followed by some weights in the basement.
So why do I feel like my throat is bleeding and my lungs are collapsing?
I only made it down the hill and back up , maybe half a mile, and as for weights.....maybe later.

So it's official, I am old and out of shape. Luckily I have some twilight delight intense dark chocolate which is proven to have some kind of medicinal qualities so I will go and "heel" myself with that.

I'm thinking I may need to try again tomorrow.