I'm a runner, usually try to run 20-30 miles per week and cross train on the elliptical or take a spin class on Mondays, and my hips have been bothering me. Do you think it's better to run more days of the week for a shorter distance, or is it better to save it up and do a couple long runs and a couple of short ones?

What are you running on? That has a lot to do with joint pain. Also, how are your running shoes? They are only good for on average 300 miles or so.
I use to run a lot. My short days were 4-8 miles and my long days were 8-16 miles. I would only not run on Sundays. It's been years and my hips are awful as well as my knees. I'm no longer allowed to run and I'm only 30. If the hip pain continues go to your doctor. I would hate to see you have hip issues like I'm getting.

I'm sorry to hear about your hips and knees! That really stinks. I love running and would flip out if I was told that I had to stop.

My shoes are very important to me. I only wear them like 250 miles or so, and get new ones. I can totally feel when they wear out, just by the way that my knees feel. Once, I tried a different brand, and my toe started to hurt and the nail turned black and fell off. Just in time for sandal season. It's still not right.

I run outside about 90% of the time. What do you think?

IMO, my 11# ds's delivery messed me up. I never, ever had a problem until he came along.

Do you have a running store that can evaluate your run and recommend shoes for you? Swimming is a good cross training activity because it's easy on the joints, especially hips. And yes, I bet delivering a big baby had a lot to do with it. If you can find a good chiropractor or doctor of osteopathy, you'd probably be better off than a regular DR. A regular DR might order xrays and end up just having you take painkillers, which doesn't really solve the problem.

Go see a really good running shoe store and have them evaluate your run as koolaidstains recommended. I'm not sure if that will help or not. You may need to go see a doctor.
If your hips are bothering you that bad something is for sure going on.
Keep us posted.