<human>: Can you provide a brief overview of the text?

I had a $7000 private loan right now and it has a $25 required monthly payment while I am in school to help keep payments down.

I decided to pay over the required payments and try to keep the total amount owed equal to the principle. Sure, it'll be a little harder now, but in the long run I should be able to pay down my loans in 3-4 years after graduation.

My problem is each month the amount I owe is more. The first month it was about $7040, then $7050, and this month $7060. I was under the impression that if in the beginning of each month period the total amount owed stayed constant, then the amount of interest applied should be the same every month. The first month I paid $40, then $50, and this month $60.
<bot>: How come the same amount of principal incurs a greater amount of interest each month, if the interest is paid off in full each month?