It is BECAUSE you have loans and no credit cards that why you credit score is low...
608 is not bad. Just not great. Having a credit card is not not as you think. In fact, a credit card is a great way to increase your credit score. It just have to know how the system works.
Look at it from the bank POV. What you have is a student (implying no salary or serious income to repay any loans), no consistent credit history (aka credit card, loans, etc), and no job. In their eyes, it is better to reject you for any money borrowing. It is safer to go with your average 9-5 Joe with a wife and children with stable income.
See bank is a business. They have to make money. They make money by loans and fees for service. Majority of it is loans. Interest on loans is where the money is at. People who get bigger loans like mortgage because they have a stable income and the bank can make money off the interest on the loans. In other words, loans are a scam. It just comes down to money. The more money they give you, the more money they get back.
For example, my credit score is over 700 because I have several credit cards, make my payments on time, and repay all my loans. However, I pay my credit card before the cycle ends which means I pay no interest. It is good for me that I paid no interest, but bad for me because the banks ain't making any money off me. It is the banks that rise and lower your credit score. My parents on the other hand is over 800 because they paid their credit cards and loans on time and when they send out the bills. They paid the interest, the bank makes money off them, and in turn rise their credit score so borrow more money which they in turns make more money off them.
You need to start building up your credit. Try a credit card. It is a short-term loan. By using a credit card consistently, you proven that you can handle larger loans like car and maybe a mortgage. The downside to a credit card are interest rate and human's greed. People shouldn't use credit cards if they can't control their spending.
You can apply for a low interest rate credit card around 7% to 9%. Pay everything on time and never late. The more credit cards you can have, the higher your credit score will be. If you want to avoid the interest, just pay off the balance (via online) off before the period ends.
Conclusion: you're a student, no jobs, no stable income, owed a tons of money in loans, no credit cards, and still young.... are you surprised your credit score is low, really?!
You can increase your score by improving your existing condition:
-Get a job
-Get a stable income
-Have wife and kids
-Have credit history
-Owned credit cards and pay off consistently
-Have loans and pay them off
-And finally willing to give free money to the banks (as long as you keep feeding the fat-cat bankers with money, they will always give you more money to borrow)