Welcome back Tony. Were you working any formal program at all or just "not drinking" during your 3 weeks? Sometimes we need extra help, whether that be Meeting based recovery, some kind of counseling, online recovery tools like SR, or any combination of the above.
Regarding your nutrition question, if your blood work came back fine I would think that any balanced diet would be fine. If you have specific concerns or feel you are deficient you might want to check back with your doctor.