With me heroin withdrawl and oxy withdrawl started like 8-10 hours after I last used it. It would start out like I had a cold, soar throat, feverish and bad anxiety, then by the next day I was nauseous and throwing up along with all the things I mentioned before... all of that garbage. It was because I used both of them heavily, and I have a really fast metabolism so drugs go through me pretty fast for the most part, especially oxy and H which aren't long acting, oxy being a little shorter acting in the IR form of course.
And what Justferfun right above me said about needles is true. I was into doing both oxy and H sniffing, smoking, eating(only with oxy), plugging, etc. Just wouldn't pick up the needle. I would say the same shit to people who did that around me, I will never shoot anything, EVER! Well long story short, I did! Because of watching all the people I used to do H with get so much higher than I was getting from sniffing and smoking it. And once I did it myself, and figured out it was much easier and not as painful as I thought it would be, I became more and more obsessed with the high and rush that you can only truly get from IVing. I haven't touched H or any full agonist opioid for almost a year now. But I am on subs and slam them too. I don't know if or when I will ever decide to stop using drugs IV, but I do wish I had never given in to my curiousity and sky high tolerance to other methods of using H, which led me to make this mistake. I just wanted to say that anything is possible when doing drugs like heroin... tolerance and curiousity can and will catch up to you after a while and make you do things like injecting it, that you said you would never do. I know I am not the only one who said they would never shoot up anything and then became a daily IV drug user, it is surprising how quick shit can change like that.
Anyways, OP I hope you can find a way to get off of H, it isn't easy, but do it while your not in full blown addiction, which it sounds like you are almost there including the fact that you used oxy before H. It will be probably be easier to kick it. But if you cant stand doing it cold turkey, which I couldn't, by all means get on something like subs or use kratom to try and get yourself off opiates, at least the stronger ones like H. I honestly haven't ever tried kratom, but subs can either be good or bad... I know from experience. I have basically traded my addiction to opiates like oxy and H to an addiction to subs at this point. If you find a sub doc who will see you, try to do the taper rather than maintanence if you can, it will be easier to kick them too and you will be a lot less likely to get stuck on them. Good luck.