Why is it that I get turned on at the thought of anything sexual, but don't have a morning wood?

Hello! I am a 21 year old healthy (neither obese nor skinny) male. My exams got over recently, and I have been at home since, which has made my lifestyle sedentary. I have gained some weight too. Yesterday onwards, I have started to do yoga and control my sugar intake.

For more than three days, I have been having sexual urges that have led to me masturbating daily. At the same time, I don't get the morning wood - I haven't been getting one for almost a month now; I thought it was due to all the exam-related stress and anxiety, but I don't get it even after the exams. My questions are:

1. What is this happening?

2. Why is it that I get turned on at the simple thought of anything sexual, be it a video on YouTube (I don't watch porn), a random person in the metro, but don't have a morning wood?

3. Is all of this normal?

4. Is masturbating daily wrong? I have also noticed that the amount of ejaculation reduces as the frequency of masturbation increases.

Thank you for reading such a long question, and I apologize if I wrote a bit too much about my recent sexual events.

Thanks once again.