1991 Acura Legend Rear wheels

I have a 1991 Acura Legend, Which I bought four years ago and the previouse owner, I guess he was racing the car because it was droped a few inches. Know the rear wheels are going bad, every 2 months I have to change the back wheel because the thread keeps finishing quick and when I look at the back whhels from a distance you can see they are side ways, what can I do about this or waht I can buy to help the rear wheels. Thank you