Gggddd,
How did you kick heroin the first time around? What worked for you then? Can you access those resources again?
I don't know much about heroin, although oxycodone was my drug and they hit the same neuroreceptors.
Since you are a long term user in the past, I wonder if you've tried a methadone clinic, or maybe suboxone? Right now, the H has you in its talons and it can only get worse if you don't cut it out right this minute.
Your 4 year old daughter needs a dad that models "normalcy." Even though you don't live with her, she sees you and knows you are an important figure in her life. Little kids learn their perspective on the world from what they see around them. Are you a strong male figure in her life? How will she view men later on, based on the relationship she sees with you and her mom? Do you model "normal" behavior for her, or does she see the worst side of you, perhaps arguing with her mom. Be very very careful. Your kid has only one chance to be a kid in this life. Protect that and be a real dad. I mean a REAL dad. Think about it.
Ultimately, as with all addiction, you will continue to use until the desire to be clean outweighs the desire/need to get high. I get addiction. It's not so cut and dried, but you've got to make a choice to be a user, or NOT be a user.
Become a non-substance abuser, a non-substance user, not just a "paused" user. Lots of people who abstain from substances never get to the mindset where they will NEVER use again. Once you've seen where addiction leads you, and you understand that eventually there is no "up" side and only "down" sides to using H, you have enough information to make a choice.
Think of your little girl, and make the right choice.