It seems to be harder to take right turns than left(takes more pressure). Why is this? I have powersteering as well.

 

How much harder? If your tires look ok with no weird wear patterns, its prob a problem with the steering system. Possibly a bad baffle in the steering rack, I dunno. Im not too familiar with the power steering systems.

 

Are you fat?

Right turns are generally more difficult to execute under hard driving because of a weight bias to the driver's side. Like that in all cars, but it's not generally a hinderence.

As said, check for odd tire wear patterns and look for anything out of place with the suspension. You might also want to have your alignment checked.

 

I've already got a wheel alignment done. I've just bought new tires. I weigh only 175.

It's not really that much harder but its noticeable

Hmm...

 

Has it always been like this, or did it just start recently?

 

Its always been like this since I've bought the car

Should I flush the power-steering fluid?

 

Did the previous set of tires have any type of abnormal wear? As for flushing, it might help, but I kinda doubt it. If it was the power steering fluid, it shoud effect it evenly.
Also, how long have you had the car?

 

sounds like a power steering problem, not an alignment prob.

 

Any unusual noises? In addition to the other responses, it could be the bearing(s) in the upper strut mounts.