It is risky to take any kind of drugs if you have schizophrenia. I think certain no-nos are amphetamines and cannabis, as dopamine has been implicated as a player in psychosis and the symptoms of schizophrenia; cannabis just fucks with the head and can exacerbate symptoms. I think the safest option for you is opioids. I really don't recommend going for the strong ones, like heroin, as that's just playing with hell fire, go for something subtle. Maybe kratom? As far as I know opioids don't really mess with the head. Definitely stay away from GABAergics like alcohol, GHB and benzos. While it may initially seem like they don't do much to your psyche, later on (and especially in withdrawal) they claim your soul and fuck you in your head. GABAergic withdrawal itself induces all kinds of hallucinations, panic, anxiety and all that. Just don't do that.
A lot of schizos smoke cigarettes. I don't know whether the nicotine is the cause or they just like the routine, but maybe nicotine can give you some relief. I'm talking about snus and the like. It is obviously a bad idea to start smoking, because it's unhealthy as fuck.
Personally I would recommend trying to find a non-drug related activity to take your mind off things. There are many beautiful possibilities in life. Taking drugs is risky especially if you have a mental illness. But if you decide to take 'em, then follow mine (or someone else's who knows what the fuck they're talking about) advice and tread with extreme caution.