The good news: a source of the problem may be identified and the therapist MAY give strategies for dealing with the absence of sex. You may or may not be the source or a source for your wife's lack of sexual desire.
The bad news: there may be nothing you can do (directly) to generate or re-ignite that spark unless there is a specifically identified behavior on your part that "turns off" your wife. You could end up with a sexless marriage (as I have). If your wife values a sexless marriage more than the threat of a divorce, you have no power. I suspect you value marriage over divorce.
One other thing, Don't give in to the self-pity party that has you not to keep yourself in decent shape. Once I realized that my sex-life was gone, I gave in to a feeling that there was no real reason to take care of myself for her sake. It can be a tough fight back. I lost 85 pounds and am less than 10 pounds away from the weight I was when we met 27 years ago. More importantly, I am actually in better shape since I can now claim myself to be a marathoner, something I couldn't do when we met.
Sorry I can't give you a simple checklist of things you can do.
The Captain
Last sex: 04/06/1997 Last attempt: 11/11/1997 W Issues "No Means No" Declaration: 11/11/1997 W chooses to terminate sex 05/1998 I gained 60, then lost 85 pounds. Start running again (marathons)