if my husband have low sperm and drink beer and smoke weed could this give him a even lower sperm count?

Yes, it could. That being said, if being drunk & high by itself could prevent pregnancy, half of us wouldn’t be here. If you two are trying to have a baby, then he should probably at least lay off the weed. THC builds up in your brain & reproductive organs and slows them both down a bit.

Alcohol shouldn’t be a problem, but marijuana is a BIG problem. It diminishes sperm count & quality and even if he were to stop tomorrow it would take 2-3 months for healthy sperm to appear.

But I think you have bigger problems to worry about. Your husband is using illegal drugs and wants to be responsible for another human being?? He needs to get a handle on his situation first.