One of my friends had the implant in for 18 months and bled on/off for 17 of those months. It got to the point where she was so fed up that she convinced the practice nurse to remove it (apparantly they are really good at convincing you to 'persevere'!)
She was training to be a doctor at the time and made the last available appointment in her GP surgery and had it removed. She then went to the pub with her OH that night and had alot of unexpected drinks, ended up a bit worse for wear, one thing led to another and they had sex that night. As she had been with her OH for a few years, condoms were never an issue for them. She said she got lost in the moment and forgot she'd had her implant removed and yep - you've guessed it - conceived that night!
The nurse had told her to use protection for the next 7 days but that was the last thing on her mind!
So i'd say that if you get it taken out and the time isn't right to have a baby then make sure you don't forget condoms!!
xxx