Erection Problem, masturbating for 4 months now.

Dear Sir,

I just started masturbating about 4 months ago... since that i masturbating bout once to 2 times daily.... and sometimes i do it vigorously (u know wat i mean).... 2 days ago.... i notice that my erection becoming weak... and it wont last longer as usual... and i cannot easily arousable by just a little stimulant.... it getting weaker and weaker... i'm afraid that i might having erectile dysfunction... i'm just 23.... is it possible?? any advise... and reassurance... i'm kinda afraid rite now... do i need to see doctor or something?? pls guide me... what i have to do next??