>>your credit score will go up just by continuing to pay off your card in full every month>>
Actually, this is a common misconception. It is NOT always true. The reason is that far more weight is given to % of credit utilization than payment record. Understand that your credit score fluctuates constantly, based on the previous month's usage/reporting. For example:
You have 2 credit cards. One has a $5K limit, the other has a $2K limit. You like to use the $5K card because you're accumulating points or miles. Every month you average about $3500 in charges (therefore, past month expense), which you promptly pay off when due (current month expense).
BUT, to the credit scoring system, you have a $7K limit and are at the 50% utilization rate. They don't care that you pay it off; what your history is showing is that every month your utilization rate is higher than lenders want to see.
Every young person should read this webpage at The Privacy Clearinghouse website and learn how to manage their credit properly: https://www.privacyrights.org/fs/fs6c-C ... ores.htm#4
The OP should pay particular attention to "#6. You Have to Play to Score"
about three-quarters of the way down the page. It is a very clear explanation of why s/he is having trouble with lenders because of following advice that does not work in today's society.