5 year birth control

I'm 17 years old and I just recently went to planned parenthood to go get the 3 month shot for birth control -- this is my first time being on any kind of birth control-- and I did some thinking, and I know for damn sure I dont need to be having babies anytime soon. I'm not against any teen moms you guys are awesome, but my plans as far as my education and pursuing my career don't involve having a baby. I was considering getting an implant, I think it is, that lasts 5 years. My doctor said that a side affect may be that after the 5 years it might be hard to have a baby just from being on the birth control so long. This is not me saying I want a baby after 5 years, but maybe 10 years. What if I ruin my own chance of being a mother sometime down the road? I'm just really scared and very iffy about this whole thing. Ladies please help☹️