Hi - application is a tricky game. You have to try your best, but it doesn't mean you will get admitted since there are many factors, some of which we have control but some we don't.
Overall, only applying for 3 schools might be risky, after trying your best, 5-7 school should ensure you get at least one.
If you are still young, don't need to be worry, pack yourself up and give it another try.