Alphabet, what specifically occurred that made you relapse? If you want to share, that is. If your boyfriend is a heavy drinker, achieving sobriety immediately as a pre-condition to the health of your relationship may not be realistic. He may need some time to determine how to best accomplish sobriety.
In the meantime, learning whatever trigger caused you to slip (whether behavior, a particular activity, etc.) could prevent additional slips. Identifying problem behaviors/activities could help both of you stay the course until you each get fully on track.