Sorry to hear about the WD's. Oxy WD's can be a terrible time. Any WD's can be, but opiates are not fun. Luckily not deadly, but not fun.
One of the reasons that you are going through WD's is due to the amount of oxy you were taking daily (120mg). I take close to that amount daily as well, although without the Meth.
Opiates are unique drugs. To break it down, they bind to different receptors and there are 3 primary opiate receptors. Those are Mu, Kappa, and Delta. Of course there are different studies that suggest different things, but most studies show that Oxy binds to the Kappa receptor but also some to the Mu recpetor. Meth on the other hand is more of an Mu receptor.
Receptors cause a change in or release in the neurotransmitors. These are basically chemical messengers. Basically without taking opiates you have neurotransmitors that or "chemical messagers" that regulate things in your body like natural pain killers. When you start taking opiates, you are replacing these chemical messengers with synthetic or semi-synthetic substances or in some cases natural substances. Basically you are telling your body that you are have these pain killers so the body stops producing these chemicals.
When we ingest these meds like meth, oxy, etc, they work on different receptors and chemicals in the body. So if you were at a low dose of Oxy on the Meth you probably wouldn't have had that much of a problem. However, your body is expecting these chemicals at certain time, and if not, at least in the day.
So you are giving your body 120 mg of Oxycodone daily which is short acting since you are using IR. This immediately binds and spikes these chemicals in your body. Your body gets used to this amount and now requires it (tolerance). So suddenly stopping one of these chemicals (Oxy) at that amount a day, will cause WD symptoms. They would be even worse if you were not on the Meth.
Now that you are probably completely confused
You are either going to have to work through the WD's or get ahold of your doc and taper the oxy down. I suggest the latter.
I hope this didn't confuse you too much, but I wanted to give you some background on why this is occurring to you in my opinion. I guess I could have just said, "Get some more Oxy" LOL.
Anyway, I hope you start feeling better. Keep us posted on your symptoms and what the Doc says if you contact him.