I had that stupid Nexplanon implant in my arm. The first three months were great until I randomly started to get sick practically every other day, then every day, then every single night. I couldn't lay down, I couldn't sit, everything was uncomfortable in my body and I even lost weight due to this bullshit because who the hell wants to eat food when you're constantly puking your guts up. The mood swings/changes got pretty bad too, and it ultimately led to me demanding that a doctor pull the bullshit out. The E.R. first denied me because "oh well we didn't do it so it's not our responsibility", so I went to a Planned Parenthood copycat and demanded they take me in due to the fact that I was sick nearly every day and couldn't function properly.
All in all, fuck birth control. Your fiance/boyfriend is a retard if they can't successfully pull out every time. Condoms also are fine, just invest in Okamoto/Crown, they're thinner than your usual Trojan so I don't want to hear bullshit about how your dick "can't feel a thing".