Im 18 years old and I haven't had this problem any time in my life until after the first 2 days I started having sex. After those days my erections aren't fully erect as they used to be.

I haven't Masterbated since I started having sex and I've stopped watching porn. I also take zinc, magnesium and vitamin D3 supplements and go to the gym at least 3 times a week.

Any idea what's going on and how to fix it? I even tried watching porn yesterday to see if I still had it in me and I got the same semi erect result.

Edit: I found this

-- Blood flow and blood pressure. Caffeine is a known vasoconstrictor (constricts or narrows your blood vessels -> increased blood pressure). I don't have any health issues regarding these, however, I feel a little more at ease and my heart-rate has been a lot more stable. I also get to avoid stim-dick (low blood flow to your nether-regions).

This is probably the reason for my limp dick. Before going to the gym I'll put 5 scoops of coffee in half a cup of soda then drink that for the caffeine rush to go hard in the gym. I'll lay off caffeine and see if that helps also.