I am having trouble with the Photos app.

I have a 2011 macbook air with a core i7 and 8 megs of ram and a 512 gb hard drive that has plenty of space left. When I upgraded to 10.10.3, it switched my iPhotos app for Photos. Now when I run the app, it makes my fan go crazy and my processor usage goes through the roof on activity monitor. When I quit, everything goes back to normal. I have about 7000 pics and iPhoto would be slow when I would use it, but not like this. I thought Photos was supposed to be able to handle large photo libraries. I haven't heard of anybody else having this problem online. The only thing I can think of is when I started it up and it was "optimizing" or something, I ignored that message and closed it or something. But now I have let it run overnight and it shows no improvement. Thanks for any help you can offer!