How is your insulation between your ceiling and the roof?
A radiant barrier helps but it's not going to be a match for fully functioning r22 batting or anything.
And you might want to consider replanting shade trees now that the old ones have been removed. Once it's the same height as your house it puts out as much equivalent cooling as a window air conditioner, and during the summer that's money in your bank.
And honestly, since you live in Texas and you're paying $285 a month for electricity, looking into some sort of solar might be well worth it.
If you have a larger property like my dad did down near Austin, you could probably do a ground mounted solar install and save a lot of money on the installation which is where with current rates the majority of the costs go to installing solar.