Dear
Welcome to HCM
We understand your concerns
I went through your details. Please don't blame
masturbation. Masturbation is safe. It is natural and normal. Masturbation cannot directly your health or sexual ability.
If your erect penis is not as hard as before, the reason could be simply lack of sensual pleasure. Usually, in the beginning stages of masturbation or sex, the erection may not be hard enough. Once the process goes through and when it near the climax, the penis gets harder and harder. You should know this.
If you are stressed, anxious, having fear, tired etc, naturally, your sexual desire will be low. This directly affects the hardness of erection. I thing you need
psychological counseling.
Consult a psychologist.
If you require more of my help in this aspect, please use this URL. http://goo.gl/aYW2pR. Make sure that you include every minute detail possible.
Hope this answers your query. Further clarifications are welcome.
Good luck. Take care.