Hi. Thanks for your query. Noted the history in a male of 53 and understood the concerns. Sex per se is a very strenuous activity but the recovery time from fatigue can be a few hours at the most. Since you are getting fatigue to the extent that you have to sleep, and feel that your strength is gone for the next two days, mind and thinking get slow after intercourse with wife it indicates that you surely are suffering from a basic cause that is causing all these. Hence I would advise you the following in such a situation: Consult your Family Physician for a thorough clinical evaluation, examination and investigations as per the clinical findings. These can be: Tests of blood for CBC, sugar, HbA1c, thyroid, liver and kidney functions. Tests of urine. Primary X-ray chest and Ultrasonography of the abdomen. Any other specific tests. All these together will give the proper diagnosis to give you a plan of further management. Til then take Multivitamins and healthy foods. Stop smoking and alcohol or such things that cause weakness.