sub running funny?

Ok I just finished installing my new subs amp and headunit about 2 weeks ago. The sub was running perfect for a while. But today when I was on my way home today my sub started acting up. It sounded like the low-pass on my amplifier went out. It sounded like it started playing higher freq's. I have the amp set to 40 (lowest it will go) and I also have my headunit set for 50. I drove the rest of the way home and all of the sudden the problem went away. Sub started hitting the super lows great. Then it started to clip bad so I so turned the sub off on the head-unit till I got home. Once I got home I opened up the trunk to take a look at the sub to see what was going on. I look at the sub as it is hitting (at this point the sub sounds like it is hitting just fine) but it is not extruding it is sucking itself in and bottoming out very hard. Right after it bottoms out it extrudes itself to the max and clips like crazy. I only have the volume set to about half where I normally listen to it at. I have changed nothing in the weeks since I set it up and have had no problems up until now. It is a l7 12 in a sealed box getting fed I'm guessing around 800-900 rms. The amp is a pioneer 600 rms at 2 ohm. The sub is wired to 1 ohm so the amp is pushing a little more since it is wired down to 1 ohm (and taking into consideration power loss) Now the amp says it is only stable down to 2 ohms but like I said I have had the sub set up this way for 2 weeks with no problems. Has never went into protect. On a note I looked at the sub hitting when I got it all hooked up and it looked perfect nothing was wrong until now. Thank you for any help I just cant figure out what might be wrong with it. I'm stumped. Fyi I have built sub boxes and set up systems since I was about 15 and I am now 26 I know a few things but I am in no way a master lol. So I know for a fact that everything is wired properly.

Sounds like you blew your amp.Support the12volt.com

see thats what I kinda figured being its not the best amplifier for the job but idk. Im on my way to work in about 10 min and its a hour drive so ill find out if it works fine or not. Although I should look into getting a kicker 750.1 for it but don't want to spend that kind of money atm Thanks for all the help.

I dont think that amp is 1 ohm stable, try it at 2 or 4 ohms.