Firstly, you don't 'need' a girlfriend at all. You may want one, but needing and wanting are two different things. If you feel that sort of 'need', then there is more likely a problem in your walk with God that you are not allowing Him to fulfill you.
Also, if you're struggling with sexual issues without a girlfriend, why do you think it would be wise to have a girlfriend? A girlfriend would be nothing but temptation.
The last thing you need right now is a girlfriend. What it seems your greater needs are is to strengthen your walk with God, and focus more on adjusting to school and doing well in school.
As far as what it will be like in college as a Christian, that's tough to answer for anyone not living in Kenya, or wherever it is you plan on going to school. Experiences in the US may be different than in Kenya, so it can't really be answered by most.
Temptations are best fought through scripture. When Satan tempted Jesus, Jesus resisted Satan's temptations using the scriptures. So learning scriptures that apply to your temptations and then resisting the temptation by saying those scriptures is the best way. Also, reading our bibles helps to strengthen our spirit, renew our mind and help us have more control over our sinful bodies.