Abby, trying to find out what is going on may mean asking your doc to do some stool tests. They're done every day for a variety of conditions, so there's really no need to feel that there's anything strange about asking for some help. Believe me, hundreds of thousands of stool samples show up at labs every day. It could be nothing, but it's better to have it checked out to make sure it's nothing.
I do take some meds. Metformin is the largest pill I take, all others are very small. These 'pellets' are twice the size of the largest pill I take.
Are you taking any medications? Some meds don't completely dissolve in the system and can be found in the stool.