I suggest you approach a priest and ask him to be your spiritual adviser. In response to your question, there is a point where an addiction becomes venial sin. Remember that mortal sin requires full consent of the will and addiction means you are no longer fully consenting to it. I recommend regular confession. I go every week. While confession is for reconciliation, it also helps you grow in love for our Lord and strengthens your will. If you do not already know the prayer to St. Michael, learn it and use it! Buy a jubilee medal of St. Benedict, have it blessed and wear it always. It is inscribed with prayers and has been used in exorcisms. I know it helped me the second I put it on(especially since I was tempted that very night).
Also, try the first Friday devotion to the Sacred Heart of Jesus. He has given me the strength to overcome my addictions, and of these I have many. Attend Mass and receive communion the first Friday of every month for 9 months straight and He will help you, especially at the hour of our death. Also spend time in adoration and consecrate yourself to His Sacred Heart. I’ll light a candle for you at the perpetual adoration chapel close to my house.