You shouldn't be doing drugs& endangering yr health- so I hope you've completely stopped, especially now yr pregnant.

But yr doing drugs is not an excuse for your boyfriend to cheat; he could have given you an ultimatum or left you if he was unhappy.

Now, yr carrying his child. If you believe he's not going to be unfaithful again, and you want to forgive him, that's up to you. It might be a good idea to go for counselling. If he's serious about you, does he want to marry you?

I wouldn't advise you to be quick to trust someone though who won't own up to his mistakes and puts the blame on you. If he won't admit he too was in the wrong, it would be better to leave. But by all means, if you believe the relationship is salvageable- and you want to salvage it for yr sake and yr unborn baby's, then by all means do so. Just be sure he is truthful with you now & get professional help. Good luck.