Sims Pets Lags and Glitches

Okay, so I've had a huge problem with my Sims Pets game after I downloaded it. I bought it off origin as a download installation (apparently that was a terrible idea) and I downloaded. It took 3-5 hours to download (it never takes that long on a disc). But afterwards it was fine. And I played with it for a few weeks or something and everything was great.

Then I make my character go on vacation (I have world adventures extension too), but she's rich so I exited after a day because I got bored and that's when it turned upside down. First of all, my horse glitched and turned invisible. Kind of neat except it began to starve and stink because I couldn't click it. Then my character's boyfriend turned into a female centaur. Which was funny until it didn't go away. And then I exited the game because... I didn't really want to play anymore.

And then the next time I log on it's slow. I mean, 1 minute to load a mouse movement kind of slow. And not only that but it wouldn't open my family anymore. And I lose all my stuff. I tried duplicating it to see if it would work, it did. It loaded the family, issue ? There were suddenly two of the same character, the horse was still invisible, and the boyfriend still a female centaur. Great. I decided to start a new family to see if it would work. Made my guy and it was great. Except it was still really slow. I gave up after that.

I tried again after a few months like usual. Uninstalled everything and reinstalled the Sims game, without the pets extension, it worked fine. No centaurs, no twins, no invisible pet, no lag. Fabulous. Then I tried the pets extension again, because I love animals, and bam, huge lag again. Takes 4 grand hours to download too.

Now ? I don't know what to do, I want to play with animals since I paid for it. But it just screws everything else up. Anyone have any suggestions ?