JD, you could be describing my son in your story, he always did well at rehabs and managed to stay sober when he got out for a period of time, once even 3 years...before he relapsed and the revolving door went round and round.
Your boyfriend has shown a pattern. Few addicts get clean for good their first time around, but many go on for years and years (my son has been 20 years or more) and what you need to decide is if you want to live a life of wondering if and when the next relapse may happen.
WE don't make it happen, we don't stop it either. My son relapsed on the best days of his life and he relapsed on the worse...it's just the nature of the beast of addiction.
I would suggest finding some meetings for you, to help you regain your balance and to see with clarity the life you are living.
Hugs