Why do I not get hungry till I smoke weed? I been smokin weed since I was 13 and now I can't eat till I smoke why is that

You're addicted. Sounds like you've unfortunately become so addicted to marijuana that your brain doesn't think it can function normally in its absence. This is a serious problem which requires help. Please seek an addiction counselor and get help.
Learned association. It is likely that for you, the cannabis is acting much like the bell that stimulated pavlov's dogs to salivate.