2003 Honda Element Timing Belt

2003 Honda Element 120000 miles

I accidentally let my 03 Honda Element get very low on oil (still on the stick, and no oil light on, but pretty low). The car started acting weird: once the engine warms up, if I try to accelerate hard, it won't respond, it just slows down. Even if I accelerate slowly, it will only let me get to 70mph and then it immediately starts slowing down until it's down to 60. If I only accelerate slowly and I keep it below 70, it acts fine. I've refilled the oil, but that hasn't fixed the problem. Does anyone know what might be wrong with it or how much it might cost to fix? From doing some research on my own, it sounds like it might have "jumped timing, " but I don't know what that means. Will I definitely have to replace the timing belt, and have all of the valves checked, etc?