Questions about running shoes?

I recently got some new running shoes, and I'm afraid they are the completely wrong kind for my feet. I'm looking for some advice from anyone who knows very much about running shoes. I'm just starting to really get into running so I'm not very knowledgable about it.

Previously, I had been running/exercising using Asics Gel TriNoosa 8 women's running shoes (links below, if it helps). Honestly, I bought them for the pretty colored design rather than the type of shoe. They were pretty comfortable, but I noticed after running very long the outsides of my feet (opposite my arch) would become very sore. This would be lessened by loosening the laces, and improved as the shoe got more broken in. The shoes are suggested to be neutral or for very mild pronation.

I recently went to get some new shoes. After explaining my sore feet problem to the employee helping me, he said it sounded like I underpronate. However, when I got on the treadmill so he could see how I run for an entire 10 seconds, he said I overpronate and showed me the video (I saw no overpronation or anything but a straight ankle to be honest, but he's the "expert"...) He recommended a pair of Brooks PureCadence 2 shoes that were on sale, and they seemed comfortable enough, so I bought them.

However, since running in them, they KILL my feet. The outsides of my feet start hurting so bad I can barely wear the shoes any longer. It even happens when I just simply walk in them for more than 10 minutes or so. They fit very snugly so I can't loosen them like I did with my old shoes. With my research online, this still sounds a lot like underpronation, especially because I have very high arches. The shoes feel like they force my feet to run entirely on the outside of my foot because the arch part of the shoe is very bulky. It sounds like these shoes are recommended for extreme overpronation from the reviews. I'd love to return them and try something else, but the receipt said that they did not do returns or exchanges on anything that had been worn or had tags removed, and I think my boyfriend may have accidentally thrown out my receipt anyway. I'm stressing because I really cannot afford another pair of shoes right now, but these are horrible.

Any advice on what the problem might be? I'm very sad that I went through the trouble to get help picking out the shoes and yet they hurt my feet much worse than my old pair.

http://www.amazon.com/ASICS-Womens-GEL-Noosa-Running-Shoe/dp/B0088WT4V8
http://www.amazon.com/Brooks-Womens-PureCadence-Lightweight-Running/dp/B0089H6Y4W