Early 20s, but bonking gf or watch pawn , kj is soft. Help?

[Abuddlah]

In early 20s now , been bonking my gf for 2 years now. Starting very song, kj hard and no problems. Recently kj like BO feel, at first gf BJ HJ me, sibei hard. Then bonk halfway will lose erection then become soft and hard to finish.

Then I thought maybe need to eat some supplements then went to GNC to buy zinc supplement. At first my kj got back its glory days but then now become same problem. How?

I watch pawn also same leh. Please help! I'm like too young to be suffering