Uy, normal yan first month pa lang kasi ang body mo is adjusting sa hormones, a few of us tried injectables at lahat nag-experience ng cramps or spotting in the beginning, so don't worry! But since it's been a month na at it's still bothering you, better check with your OB just to be sure it's nothing else, kasi everyone's body reacts differently sa contraceptives at they can give you better peace of mind or maybe adjust kung kailangan.