How can I lose more weight?

I have been working out and dieting for about a month now. In the first week i lost 10 pounds and was ecstatic. But for the last 3 weeks i haven't lost any weight. I have actually put another pound back on. When im at the gym i usually split my time between cardio and lifting weights. I was wondering if there is something i should be doing differently like cutting down on lifting and doing more cardio or taking some supplements.