How do I (27f) tell my boyfriends (27m) parents about his mental health / drug problem?

I have been with my boyfriend for over 5 years. We have been living together for 3. We share a house and 4 cats.
About 3 weeks ago he suddenly started acting aggressive (only verbally) and erratic. He ended up pretty much kicking me out of the house.
Whenever I asked him to talk about the situation he would either start laughing maniacally, giving me made up reasons, or threatening to go back to using drugs regularly. He also disappeared for a few days while I was on a business trip, neglecting our cats.

A little backstory, when we first got together in college he had a bit of a problem with stimulant drugs, I was able to help him get out of it, and since then he’ll only do them 2-4 times a year at parties that I also go to with him. Even now he can’t control himself too well with the drugs – but I thought that at least he does them rarely and with someone who will take care of him.

Back in 2019 he had an episode which was almost exactly the same as what’s happening now. He suddenly became very mean, narcissistic, erratic, and started engaging in risky behaviors (excessive speeding, drinking, drugs). This lasted around 3-4 weeks, after which he totally changed for the better.
Before he got better he had a dangerous overdose, I think that’s what brought him back down.
Most of his friends didn’t notice he was even going through something like this.

I was young and stupid at the time so I decided to take him back. It was a very good relationship, and I even forgot that any of that happened 4 years ago… until this month.

I have moved out to my parents, and notified his aunt (who did not take it super seriously, but agreed she’d take care of the cats if need be). I feel like I also need to tell his parents. We were very close for the past 5 years, seeing each other multiple times a week. I feel like they are the only ones who can actually do something.

All of my furniture is still at his house, I won’t be able to get it for another month because I have back to back business trips planned.

I don’t want to wait that long to talk to them, but I am also worried I will never get my things back.

I think they deserve to know, they’re smart people and I think they’d want to help their son.
How do I go about talking to them? How
much do I share? Should I meet up with them?

Maybe I can have the aunt join?

tl;dr: boyfriend is going through a scary episode and i’m not sure if/how to let his parents know.