There are numerous causes for your problem. Main cause of foul smell or urine is some urinary tract infection. Those who are suffering from UTIs usually have pains, foul smelling urine and frequent urge for urination, colored urine and cloudy or bloody looking urine. Dehydration is one another major cause of foul smelled urine in youngsters like you. Make sure that you are drinking a lot of water every day. Take a minimum of 12 glasses of fluid including water, juices and fruits. Dehydration causes urine to make it more concentrated with wastes, which naturally cause foul smell to urine. Also, reduce drinking alcohol and caffeinated drinks like coffee, which cause dehydration. Go for a urinalysis if you still get the same issue, even after following the aforesaid tips. Take care.