Erection Problems. The main concern!

I started masturbation at the age of 16. I used to do it thrice a day for the first six months after that I reduced it to three to four times a week. But I used to do stress coz i thought that I had committed a sin. I started facing soft erections and premature ejaculation At the age of 18 I consulted a doctor he prescribed me a course of addyzoa and multivitamins with some injections. He also gave me a course of Musli plus too. Later I started masturbation at the rate of 2 times a day for 6 months but stopped it later. I was stressed and again consulted a doctor who prescribed some medicines and told me not to take stress. But I have been under a lot of stress since the last 2 months. I have been masturbating thrice a week. Is it harmful. Should I stop it. Or is stress the main concern