How much is too much???

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Ok... I have been working out regularly for well over a year. I do Zumba classes 3-4 times a week. I ha e gotten many of my friends to go with me. I love it and the changes in myself it has made. So recently I convinced my best friend to try it, but the only time she can go is during the day and I enjoy going with her, but the classes are not good enough to replace my AMAZING evening classes... So on top of my normal 3-4, I have added 3 more to my schedule. They are on different days except Friday's, I have 2. I'vs been doing this for two weeks and it hasn't been a problem but I don't want to over train. My muscles feel tired, but not any worse than when I first started over a year ago... I am thinking my body will adjust to it. By the way, I am already at goal weight and maintaining which means I have had to majorly up my daily calories.