It seems like your choice of parametric distribution is not appropriate for your data and it seems that you might be approaching the problem in the wrong way.
First things first... What are your data? What is their physical meaning? Do they have lower or upper bounds? What do you want to do with the distribution fit? Have previous analyses (by others) justified the use of a exponential or chi-squared distribution? All of these questions will help you to decide what type of distribution is appropriate to fit to your data.
Second things second, fitting... Do you have Statistics Toolbox? If so, then dfittool is a good place to start. In command window type
doc 'Model Data Using the Distribution Fitting App'
and choose the first option.
If you can provide us with more info about your data we can probably help some more.