Insomnia. could it be withdrawal from the oxycodone even though i didn't take it that long?

Absolutely: Melatonin or camomile tea can help. A lavender sachet near the head of the bed can be soothing as well.

Yes: Yes, opioids disrupt sleep-wake cycle. Usually it is temporary problem. Try solving it by simple recipes: no carbonated beverages or coffee, instead hot herbal tea with honey; hot shower or bath before going to bed; no tv in bedroom. If insomnia continues, melatonin or short-term administration of sleeping pill may help.