Couldn't agree more with the other 2 posts.
If you are going to have sex then you have to be capable of accepting the risks of parenthood.
Ask yourself (when sober and straight - not saying you aren't but for any others that may read this for advice). Look in the mirror, look yourself in the eye and say "am I ready for sex, is this what I really want?" if you can say honestly to yourself the answer is yes - then perhaps you are ready.
If you think maybe I am, I might like it but... Then you definately are not ready.
Good luck be strong
kia