I don't know what exactly it could be, and since you too are suspecting an STD, my advice is to better have a doctor to check this.
yes there is skin color alteration. it has been there a little over a month. it is not painful. i am sexually active. i was wondering if it could be an STD
> there is a white line from the base of my penis to the top
Is this some skin color alteration? For how long it is there? Is it painful?
> after ejaculating clear fluid runs from my penis. occasionally it runs without ejaculation
I would say that this is the pre-ejaculatory fluid, but as its name suggests, this comes out before ejaculation.
Are you sexually active? Any suspicion for STD?