Alernate Formula

Hello! I'm looking for advice on an alternate formula that may be able to do what I want, with less hassle.

 

So I have a budget workbook, and each month is on its own sheet. On another sheet I have different stats to track my spending and trends.

 

I have a column that shows me the average spending in a specific category from the time I started the budget, until the current month. The formula I currently use is as follows:

 

=AVERAGE(September!C45,October!B39,November!B38,December!B50,'January-18'!B54,'February-18'!B50,'March-18'!C51)

Now, this works, but it is a pain every month to add the next month, and the Row isn't always the same because some months I add different categories. Also, the formula is getting longer and longer and will continue to do so which is just unpleasant to look at and annoying to scroll to the end of to add the current month's field info.

 

So my question is this: Is there a formula out there that will do what I want, but a little more simply and more automated?

Something perhaps that will:
1) look over a range of sheets (e.g. September-current month) to find the matching category. (In column A) I have no problem with manually changing the end sheet name each month.

2) Average all values in the adjacent column. (Column C)

3) Output the average on my stats sheet.

I hope that made sense... Thanks for any help you can offer.