Either you or your insurance company can decide not to renew the policy when it expires. Depending on the state you live in, your insurance company must give you a certain number of days notice and explain the reason for non-renewal before it drops your policy. If you think the reason is unfair or want a further explanation, call the insurance company's consumer affairs division. If you don't get an explanation, call your state insurance department.
The company may have decided to drop that particular line of insurance or to write fewer policies where you live, so you shouldn't necessarily think the non-renewal is because of something you did. On the other hand, if you did do something that raised the insurance company's risk considerably, like driving drunk, the premium may rise and you may not have your policy renewed.
You can find out from your insurance company more about why they are not renewing your policy with them. If it did not have to do with your driving record or any serious offense than you should be able to get insurance elsewhere without it effecting your rates. If it is due to a serious offense or bad overall driving record or too many claims then it may make it harder to get insurance or will result in you paying more with a company that will insure you.
So if your insurance company does not renew your policy, it does not necessarily mean that you will be charged a higher premium at another insurance company. What you can now do though is shop around for auto insurance elsewhere. If you would like to find a new insurance company you can get a direct insurance quote here.