Is masturbation healthy when you are 19 years old?(female) why does it take me a long time orgasm?

Yes: Masturbation is healthy at any age. It is also important to relax and not worry about it. Think of it as a healthy part of your routine. Don't worry about how long it takes. Everyone is different. Do some reading about healthy sexuality. There is lots of info on the internet.

Not unhealthy!: There is absolutely nothing medically wrong with masturbation, but plenty of religious and old-fashioned ideas exist that can make one feel "guilty" about it. That's also probably the reason it's an effort for you. If you are ok with it then free yourself from the "stigma" and learn what feels good. You will be a better partner if you know what you like and communicate this when ready! practice!

Orgasm: You did not indicate whether your taking a long time was during masturbation or other sexual activity. If this was with a partner, perhaps they are not stimulating you adequately or using the proper positions. If this is during intercourse, perhaps a longer period of stimulation prior to sex would help. You might consider seeing a sex therapist.