Every birth control option affects women in different ways. For me, the arm implant caused several side effects that I did not need in my life, causing me to quickly regret the decision I'd made.
1. Irregular periods
In my experience of having an arm implant, my periods happen more frequently. In my first month, I had no period. The rest of the time, I had two periods a month — one normal period and one with old blood. Sounds weird and gross, but yes I had two periods a month— meaning two out of four or five weeks were miserable.
2. It hurts and takes longer to heal than any other birth control
Sure, the IUD, birth control shot, or other forms of birth control hurt going in at first. Yet, the implant hurts for a longer period of time compared to others. With the IUD, you feel pressure or subtle pain but after a few hours or a day, you heal. The implant is different. It hurts going in, but you bruise immediately after and it takes a while to heal. Truthfully, I do bruise easily, but my bruise hurt three days afterward. Not only that, but the bruise took about a week and a half to go away completely. Any other birth control wouldn't hurt for that long. Also, the implant will tend to feel itchy from time to time, the next few months at the point of insertion because your body is still adjusting and healing internally. Altogether, it takes longer to heal.
3. Weight gain
To be fair, almost every hormonal birth control has this side effect. However, I did gain weight with the implant and once I had it removed, my GYNO said due to weight gain, it makes the implant harder to get out. Thankfully, I didn't gain as much as my GYNO expected, but to know weight can affect the time to take out the implant is also another reason you don't want to get it.
My experience with the Nexplanon was unpleasant. But other women swear that it works for them. The best way to figure out which birth control works for you is to test each option. But carefully read the side effects because Nexplanon has several — more than most. And the most severe side effects can result in having to surgically get it removed or other potentially fatal consequences. Avoid the implant if you possibly can!