Also, I had the huge bruise for about a week and a half and mine didn't hurt at all except for the bruise being tender. 

I've had mine for 8 months and hate it. I get a heavy period every month that lasts 3 weeks. I'm planning on getting it taken out before I leave for college in September. I haven't gained weight onit though. 

So I got nexplanon and mine only hurt for about 4-5 days. So far I haven't gained any weight.

I've had mine for over 2 months now and I love love love it. Everyone handles birthcontrol differently as I'm sure you know. I haven't had any crazy side effects from it except random periods. The weight gain that your friend had could easily be from the fact that the nexplanon makes you want food more. So as long as you watch what you eat, you shouldn't have to worry to much about gaining tons of weight. 

I love mine and it only hurt for maybe 3-4 days.