I think he is in bad relationship with her, he didn't answer the phone when she calls, and in one of the episodes he visit her just for a couple of minutes, why is that?

Its funny in the earlier episodes after Chrissy is shot and hes at the hospital his mother doesn't look much older than Adriana.

But a few seasons later she's played by a totally different character who looks the right age to be his mother.

His mother was an alcoholic from what i remember. But then Chrissy was a bigtime junkie anyway so doubt thats an issue.

The two were estranged from each other ever since the death of Dickie Moltisanti.

He called her a "fuckin whore" during the intervention, lol. He probably blames her a little bit for his own alcohol addiction and battle with drugs. I mean, both his parents were addicted, and it's not unlikely that he blames them a little for taking that same route.

It's not the first time The Sopranos makers have decided to swith characters. Good observation ukwiseguy.