No, you have hormones. Just because you are “obsessed” with someone does not mean that you have OCD. In fact, if having a crush on someone and dreaming of him or her meant people had OCD, almost the entire population would have OCD at some point in their lives.
This is very normal behavior, especially while going through puberty. It is very common to develop very strong feelings for people very quickly, only to have them dashed a week later, and then to develop a crush on someone else the next day. This is just the way our brains and emotions work during adolescence. But this can also occur as we age. Married people may meet someone else and find it difficult to get that person out of their head.
Parents often think of their children a great deal, especially when they are newborns, but we would not label this as OCD either. Therefore, thinking of people and dreaming of them does not constitute an obsession in the OCD sense of the definition. Obsessions must be intrusive, and rarely do adolescent girls find thoughts about the star football player to be intrusive, in fact, they seem to enjoy it and tell all of their friends about it. Most people with OCD would not do that. In fact, individuals with OCD would attempt to neutralize the thoughts, and rarely does someone with a crush try to stop thinking about the object of his or her affections.
Some people wonder if OCD can lead to stalking behavior. Most likely this would not happen, for the simple reason that people with OCD do not want to get caught or draw attention to themselves. It is possible that a person may have intrusive thoughts about a person, but taking that to the much higher level of stalking goes beyond OCD and probably into the realm of a personality disorder or some type of psychotic behavior.