You've lost the weight; tough to accomplish, but you got it done. Now it's time to build a strong muscle base. Start adding some light weights to your core exercises, if you haven't yet. Increase your time with weights. I'd recommend a 60/40 (weights/everything else). Not sure what your routine is; but it sounds like you're committed, and after a month of muscle building, you should notice results without losing much weight. If you like what you see and want more, repeat or push to a 70/30. Ive been athletic majority of my life since middle school. 7 years of consistently working out now. Sometimes i see a 6 pack; and some weeks its just one solid pack. So stick with it and remember its what you feel that counts.