Increasing your doses of opiates and switching to more potent drugs to get the same feeling are the first signs of the slippery slope that leads to addiction.
What kind of pain is it? short term or chronic? You've already been taking them for months so I assume chronic. Is pain the only reason you use, or do you get high as well/ use it to deal with anxiety/insomnia/boredom?
I highly recommend you do not switch to oxycodone from hydrocodone. In a few more months you'll be asking about Opana, then a bit later, about heroin (but you'll just snort it), and finally you'll end up on the needle. I've seen it happen to myself and so many people, including many who were prescribed them for legitimate pain. Having a drug be medically useful to you does not mean that its other effects don't apply to you. No drug I have ever encountered is as insidiously addictive as opiates. Many people don't realise they have a habit until they run out and feel withdrawals for the first time. When I first used opiates I would take 3x 5mg vicodin and be high. When my heroin addiction was at its worst I was IVing 2-3 grams of high quality heroin every single day. It didn't get me high, It wasn't fun, it just kept me from being violently sick from withdrawl. No other drug has the addictive potential of opiates (greater % of people who use them become addicted than with any other kind of drug).
I don't know your situation, but I feel like I should try to explain how easy it is for opiates to take everything away from you without you realizing until its too late, and its best to be aware of the risks when using drugs this dangerous. As my addiction progressed it didn't even register to me as a problem (until I was so deep in it was too late to stop) which I partially attribute to the general content feeling that opis give, which makes it easy to ignore things that would normally make you think twice and cause concern.