What Causes A Clog On The Top Of Penis Head?

I was having sexual intercourse about three weeks ago and couldn t ejaculate , I noticed a bludge or a clog on the top of my penis , it is on eather an artery or maby where my sperm comes out it doesn t hurt but it s really stressful , I have been taking sexual stemulants to have better performance , also I have been using meth as we ll , sometimes it s like I go knumb from the waste down please help me