Marijuana and alcohol are commonly mistakenly believed to increase libido, but they both actually do the opposite. If you do it once, it might (because of expectations, interesting psychology to that), but over time it will make the problem worse.

Take it from someone who has a partner who uses one, so knows.

OP, porn addiction can definitely cause this problem. It's, actually, rather common with porn or masturbation addiction. It can make a person anxious in real life sexual encounters. It's definitely something a therapist may be able to address.

In the meantime, I highly suggest other ways to be intimate. If he's not comfortable with sex or blow jobs, find something else. Keep trying things, until something makes him comfortable. If he just wants to pleasure you, try to be okay with that until he can work on this. There are other ways.