Well brother, don’t worry. This is quite normal. There are two small structures attached to the urethra (a passage running the length of the penis which carries both semen and urine to the tip of the penis) which are called Cowper's glands. During sexual arousal, these glands may secrete a clear, mucus-like substance called pre-ejaculatory fluid, or pre-cum. While the purpose of this fluid is not known, and the amount varies from man to man and from one sexual experience to another, pre-cum may contain some sperm. A partner could obtain an STD (including HIV), or could become pregnant, if the love drops come in contact with their partner's mucous membranes. There is no way to "control" pre-cum, except to avoid sexual arousal.