Only getting 22-23 MPG

[SWICKENSJR]

I know this is long so please bare with me and read it, I could really use some insight...

Ok, so I bought a used 2007 yaris sedan with 52,000mi (everything is stock except the aftermarket rims on the car look a little wider than what I've seen on other yarii) and have been watching the fuel economy from the get go. I fill up, reset the odometer at the gas station and drive away, when the last bar starts flashing I fill up again and divide the number of miles driven by the amount of gallons filled. But I've noticed that the last two tanks averaged were ONLY 22 and 23 mpg or about 220-230mi per tank?!? I'm seeing everyone getting 35-40 mpg and it's stressing me out that something is wrong with my car. I had it in the shop right when I got it for a fresh oil change and had the toyota dealer do a "gas 1" fuel system cleaning treatment or whatever it's called. The car seems to drive fine and doesn't seem to drag or hesitate and has no CEL. The alignment does seem to pull to the right a little though.

My driving habits are as follows:

I only drive 4 - 2.5mile trips a day during the week -- First at 5AM (2.5 miles to work) then at 11AM (2.5 miles back home for lunch), 12PM (back to work), and 5PM (home). During these trips it's all city driving with about 7-8 lights in between. I'm not super slow from lights but I never let RPMS go much above 2000 (maybe 2500 on occassion) when accelerating from a light and dont go above 40 mph. It's been cold for southern california lately, ever since I got the car, about 45-50F in the morning when I leave, but I only let the car warm till the RPMs drop to 1000-1100 and then drive (usually 30 seconds to a minute). The weekend I probably only drive another 10-20 miles doing various things.

So I know short trips are bad for MPG especially in cold weather but could how I'm driving really affect my gas mileage THAT MUCH? I mean 220-230 miles on a tank is insanely low!

It's seems crazy to me and quite frankly I'm worryin. Any help is very much appreciated!