1. Stress and over-work Are the most common causes of a reduced sex drive. cigarettes, alcohol and above all, try to relax and switch off.

2. Poor diet; If you’re not getting enough vitamins and minerals hormone imbalances may arise and have a big effect on your sex drive.

3. Being overweight: Can cause sluggishness, low energy levels, a diminished libido and low self esteem. Consuming too many carbohydrates
raises sugar Level which will further lower your sex drive.

4. Excessive alcohol: Reduces testosterone production. Extreme long term abuse can cause impotence, shrunken penis.

5. Smoking: It can cause high blood pressure and bad circulation, it will also lower your sperm count. Having a high sperm count acts as a
trigger boosting sex drive.

for more details....
http://www.humblemedicals.com/2018/11/some-of-major-causes-of-weak-erection.html

Have you thought about these......

# Smoking

# Acohol

# Stress