Yeah you need to be taking a lot more kratom. Unless it's a mega potent extract or one of these 7OHM variants or w/e they are called, kratom needs relatively high doses.
I don't think even the strongest stuff is active until you take at least 2g and on an empty stomach.
Many strains will need 5 - 10 grams for good effects, so I would also suggest gradually working upwards.
You'll know when you've taken too much as you'll have an unpleasant tremor and wired feeling, and may feel sick. As long as you are gradually working up that should be the worst of any side effects of taking too much.
Hopefully you'll hit your Goldilocks 'sweet spot' before you get that point.
Oxy is a relatively strong opioid though, so I'm not sure how much use kratom will be. It will probably help at least a little bit, maybe it'll help more than that when you find the right dose and strain. Also some pregabs for a few days are likely to be very helpful too in relieving any w/d symptoms.