I'm not exaactly sure if it does anything to your sperm count. However, before you actually think of having kids there are some things that you need to do first.
1. Be clean for a lot longer than 8 days. More like a year or so.
2. Find a good support system so that you don't go back to that life.
3. Cut off all ties to that world. It isn't good for you. The more you see it the more your going to want it.
4. Find someone who is willing to keep you from going back to that. Who will love you for the person you actually are. That understands, that doing that isn't good. For you , them , or the children you may or may not be able to have.
You have to understand what it takes to do something with such big responsibilities. Being clean for 8 hours or even a week may seem like a big accomplishment to you. However, when you start putting other peoples lives in the picture. It's a whole different story. I'm not saying that it can't be done. Cause, you bet your bottoms it can. You just have to want better for yourself. Drugs are not good in any way. Especially, the one you are doing. If you are wanting kids. Then, you need to turn your life around fully.
Do web research on these things. There is a lot of info for this. For the rest, you just need to believe in yourself, and for anyone that may be in your future.
It's now that you make the decisions for the future. If you want a family and kids, and that whole life. You have to make it happen. You have to become the better person.
Not only for them. For yourself also.