My Wife Is Killing Our Marriage With Her Addictions

I am a 30 year old man and I am married to my wife whom I have 2 children with, the issue is an ongoing one. She is a drug addict and I am not. I met her when I was 23 years old and wondered why she did not have a boyfriend, she was very beautiful to me so I kinda feel for it all. Anyways we dated for about 3 months then she got prego with our first son, I found out that she was a frequent smoker then of crack cocaine. I immediately dumped her, but at the time i did not know that she was prego. After she was gone for about 3 weeks she told me that she missed her period, I automatically thought that it was not mine due to what I was told about the habits of drug addicts so I ignored her pretty much. I moved on and started dating someone else for a while and did not think to much of what my pregnant ex girlfriend was saying, I was young with a good job and was dating someone who I had a lot in common with. But she started coming around causing issues with me and my then girlfriend so what I did was instead of dragging my gf into all the madness, I dumped her. I took my soon to be wife back hoping that she would stop the drugs and that we could be a family....I did not have n e idea of how much of hold that crack has on people, the most I have done is getting pissy drunk. But she is a nice person so i was n love with her before I knew it. She had my first child which was mine after the dna test of course then things kinda slowed down, she got a job and we were fine. But then those blues aka roxys came into the picture. they are worse then crack me and her went threw hell with that I had to go to cps and get custody of my kids cuz she calmed down for a minute so i intentionally got her preg.... in a nut shell she is still using every so often and i dont know what to do...but I know what I have to do. Theres more but I have to go to sleep thanks....I thought I was the only one out there dealing with being in love with an addict. ill keep in touch