OP, How much opiates do you take on average? Is it enough to warrant a buprenorphine substitute treatment, or taper, i've allways found stopping opiates to be far more easy than staying clean and not relapsing, IMO it is better to be stable on bupe than living a "yoyo life" going up and down on pain pills. That being said it takes a great amount of courage to quit, you are probably quite busy at the moment, during the x-mas period, which is good, it helps to keep your mind focused on your objective but also on various activities i presume you have been partaking in, which brings me to my second point.
As for the DXM, there i don't think there are any physical withdrawals, but the psychological part may be difficult, this is why i would allways recommend someone who is going to get clean to plan what they are going to fill the time and void previously consumed with drugs by.
For this it would be good to get some background information on you, how old are you? are you working? studying? Single? What hobbies do you have etc.
Keep up the effort, and if you feel you're going to relapse, or have a serious craving is there anyone you can talk to, often it can just take talking to someone about how you're feeling for a bit, to get past the craving. The longer you go without the substances, the more the cravings will be sparce.
Good luck friend!