All grain batch low OG

Hi everyone,
I just got finished cooking a one gallon batch of pale ale that should have had an OG of around 1.51 but I ended up with a reading of around 1.030.
So why could this be and how can I prevent this in the future?
I did my mashing in a pot on the stove and the temp got pretty high in the very beginning by accident. Then I brought it down pretty well to the 146-152 range. I mashed out and dumped it into a strainer then spared with 170 degree water several times. I started my boil with about a 1.7 gallon volume and ended up with a little extra. Maybe 1.1.
So what could be the deal? What can I do to prevent this in the future?
Is it more about my temp control problems? If so, are there any tips on how to better control it? I've read about people getting coolers and pouring the mash in there when it hits the right temp. If that works it sounds like the easier way to go.
Anyway, sorry I'm such a newbie butnim a little frustrated.
Thanks for the help!

Also I read somewhere about adding sugar to the batch to raise the OG. I this a good idea?

NO, don't add sugar.

There are great reads about efficiency on Kai's wiki:

http://braukaiser.com/wiki/index.php?title=Understanding_Efficiency
http://braukaiser.com/wiki/index.php?title=Troubleshooting_Brewhouse_Efficiency

It sounds like you didn't really have a handle on your process. The temp got really high at first? How high? If it boiled or even came close, you destroyed your enzymes and didn't get conversion. I would chalk this one up to be a learning experience, buckle down your process and move from there. Most efficiency problems are caused by poor crush, but there's a million ways you could have gone wrong as well.