I agree with the first attorney that you should first talk to your current attorney.
You've not given any facts but you should know that judges in Tennessee strongly prefer to keep BOTH parents in the child's life and absent some extraordinary facts NEITHER parent will get SOLE custody. Usually the judge will make one parent the primary residential parent and give the other parent co-parenting time (visitation).
The answering of this question does NOT establish an attorney\client relationship. If you wish to hire me call me and we will talk about it, but as of now, I am NOT your attorney. My answers are intended for educational purposes only.
You need someone to sit down with and have a reality check. You may never get sole custody. Custody isn't awarded to the best parent, it's awarded to a parent when one parent cannot be given the responsibility of making those life decisions required of a parent.
I wonder whether you have had this discussion with your lawyer and what your lawyer has said about it. In my experience when clients say that their lawyers have done nothing in actuality the lawyer has made efforts that have not produced results to the client's satisfaction. If that is true here, then the important questions are: precisely what has the lawyer done? why were the unsatisfactory results produced? should the lawyer have done something else and/or more? is the lawyer in over his/her head? A calm and diplomatic discussion raising those questions should produce honest answers, and, if you are still not satisfied, consult another lawyer with experience in custody proceedings.
These comments do not constitute legal advice. They are general comments on the circumstances presented, and may not be applicable to your situation. For legal advice on which you may rely consult your own lawyer.