Thank you for your honesty -- and I hope your letter will encourage many to pray for those who are leaving home for the first time, whether for college, the military, a new job, or some other responsibility. You're right that once we're away from family and friends, we're often more vulnerable to temptation.
The most important thing I can urge you to do is to have a friend with you at all times -- and that friend is Jesus. If you try to battle the pressures alone, you might, indeed, fail. But God loves you and wants to help you -- not just to resist temptation, but also to become the person He created you to be. The most important decision you'll ever make is to admit that you need God's help, and then to invite Jesus Christ to come in and take control of your life. We are never alone when we know Him.
Then seek out other Christians on campus. Various Christian ministries are probably active there; look for announcements on campus bulletin boards or ask your pastor. You need the fellowship of other believers -- and they need you. The Bible says, "Encourage one another and build each other up" (1 Thessalonians 5:11).
In addition, no matter how busy you get, take time to be with God every day by reading the Bible and praying. Let the Psalmist's prayer become yours: "Strengthen me according to your word" (Psalm 119:28).