I've Been On Humira For About 6 Mo's Now For

I've been on Humira for about 6 mo's now for Crohn's (fistula's) and for arthritis. I wonder if this could be the reason why I've been gaining weight? I've talked to my nurse ambassador she said it's not one of the side effects. I've also been in more pain then usual (in other places than my normal arthritis areas) could this be Humira causing the additional pain?