Help!!

My boyfriend and I just found out we were having a baby. Today his phone kept going off and I picked it up and saw his friend had texted him being a nosey girlfriend I look at the texts to find out he was back on drugs (heroin) and I don't know if I want to stay. He agreed to go to rehab and when he got out we would work on our relationship and providing for our soon to family. I'm in desperate need of advice.