Creating rows to sum categories from a pivot table

I'm very new to pivot tables. I've got an Excel file that I put a pivot table in which creates a report form for trash found during site surveys. Users can select the site and date of the survey, and the report shows the category, details, comments and the total number of items found for each detail.
I'm trying to find a way to create a sum for each category. Ideally, it would be in a row at the end of the category. I don't think it's a field I can create in the source table, because it depends on the variables selected. I've tried using the Subtotal feature, but that's not giving me the desired SUM result, just adding lots of extra rows. I can;t seem to figure out how calculated fields work in this table.
I'm attaching a screenshot. Ideally, I'd like the row inserted at the red line, summing up the highlighted numbers above.
pivottable1.JPG

I'm attaching a copy of the file here.
The "Previous Layout" sheet shows what we used to use to manually enter the information.
"Data Collection Form" is the sheet with the pivot table that I created.

Thanks for the quick help. I forgot to mention that there is a column on the source sheet "Floatables Category Final Count" which I relabeled as Total on the pivot table. It has the total number of, say, plastic water bottles found. I am trying to figure out a way to then create a sum for each category. (The column name is a little confusing, as it is the final count for a Floatables Category Detail, not the overall Category) Ideally, this data would be a row underneath each category.

For example, in this highlighted picture, I'd want to get a total of 11.pivottable2.JPG

That's awesome with the row underneath each category, but the only thing I need to change is that it's counting the number of comments instead of getting the number from that final count category. So, for example, there's no comment for "Cigarette Butts" so it comes in as 0, when there may be 20+ butts counted.

Yes, that's the category. I know there are some non-whole numbers in there. We're trying to figure out why some were entered like that instead of a whole number. (How does one have .1 of a cigarette butt?)

YYYESSSSS!!! I can't thank you enough for your help. This was my very first attempt at a pivot table, and I was really getting stuck. I work in a smaller office and don't have any Excel people in my physical location, so I've been trying to track down someone in another office to help. I think this is going to meet what the clients want, and I'm going to get the data cleaned up and try to figure out how you did this.