Help with Pagination

I am having an issue. i don't know if it's being caused by my custom template or what...

But say I am on a page like so
/incense-oils/incense-incense-burners-and-charcoal.html

Then I see the pagination numbers 2 - 3 - 4 - 5 etc.

I click 2 and it takes me to
/incense-oils/incense-incense-burners-and-charcoal.html?p=2

ONce I am on the 2nd page (doesn't have to be page 2 just once i click the pagination ONCE)

Now when I hover over the 2 - 3 - 4 - 5 the links have become like so

/incense-oils/incense-incense-burners-and-charcoal.html&p=3

So they are adding an ampersand & instead of a question mark and therefore you get a 404 if you click the next pagination link.

I didn't update pagination at all or install any module for it. Anyone have any idea why it's doing this or where i can look into the code to fix it?