Cocaine does have some negative physical effects -- it can damage the heart with heavy/frequent/long-term use, and it tends to weaken the immune system, making your more susceptible to getting sick. Furthermore, if you smoke freebase cocaine (or 'crack'), then you are damaging your lungs as the smoke is fairly harsh. All smoke is harmful to the lungs, and though crack smoke won't kill you, it can certainly cause problems over time if you smoke enough freebase on a regular basis. Another thing to watch out for with any cocaine use -- many coke heads don't eat enough (b/c of coke's appetite suppressing effects) and so can lose weight and become malnourished (leading to hair loss, brittle nails, dull and unhealthy skin, etc). So, make sure that you still eat normally and pay attention to personal hygeine.
What are probably even more problematic with cocaine and even more so freebase usage, though, are the psychological consequences. Psychosis, addiction, agression and violence (esp when coming down, or craving the next fix) can all result from cocaine use.
Despite the fact that cocaine is not physically addictive, it seems to be extremely psychologically addictive for many people, so if you want to avoid addiction (which you seem to have a tendency to, already), then be very careful about your usage. Moderate it carefully; don't let yourself do too much or do it too frequently. It IS possible to use cocaine without becoming addicted or suffering too many negative consequences, but only if you use will power (or don't like coke

).
Good luck, and watch out for yourself...