Your question contains the answer. Yes, Arkansas is an "at-fault" divorce state, with the only exception to that being 18 months of continuous separation. Since you have not been separated for 18 months, he cannot use that as the grounds for his divorce. Divorce requires grounds, and without grounds a divorce cannot be granted.
He will have to prove some amount of "general indignities" that you have done to him. There are cases on this explaining generally what is required (could be disrespect in front of others, talking down to him, yelling, fighting, etc.)
You should probably hire a lawyer to represent you in the matter, unless there is some set of circumstances that would make the divorce so easy you don't need a lawyer (word of caution - that's pretty rare, and even in those circumstances a lawyer usually makes it easier).
Usually grounds are not such a big deal. In Illinois we have mental cruelty which must be like general indignities. The lawyer will ask your husband something like "Did your wife use abusive language?" or "Did you frequently argue?" or "Did she leave the home for long periods of time?" All that is just to get past the requirement of fault. Much more important are property issues, maintenance issues and custody/ child support issues. You should have a consultation with an attorney at the very least and retain him/her if you anticipate a dispute.
The information provided herein is general information only and not legal advice. The information provided herein does not create an attorney client relationship and is not a substitute for having a consultation with an attorney. It is important to have a consultation with an attorney as the information provided in this forum is limited and cannot possibly cover all potential issues in a given situation.