Thanks for posting your query at DoctorSpring.com
I have gone through your question in detail and I can understand what you are going through.
The fact that you are able to perform sex and enjoy sex all the day except in the morning suggests that there is no organic or biological cause for the same and there is nothing significant to be worried about. The problem is psychological in nature and has probably something to do with your work stress. Morning is the time when you are supposed to get ready and move for work and if something is stressing you out at work, then obviously you wont be in the best of the moods in the morning. This gets down your sex drive and interest in sex as well.
Analyzing and sorting out the stress at work is a solution to your problem. Other wise there is nothing much to worry about . You can try cutting down your smoking. Although your current problem is not related to your smoking but in long run , smoking can effect your sexual drive by producing erectile dysfunction.
Hope I am able to answer your concerns.
If you have any further query, I would be glad to help you.
Wish you good health,
Dr. Srikanth Reddy M.D.