Husband won't have sex with me

since I got my depo shot. He kept telling me that I need to get on birth control so we don't get pregnant again too soon. (Our son is 10 months old.) We had been using the withdrawal method. I scheduled my shot appointment and that was 3 weeks ago. He won't have sex with me since I got it. I have asked him and he kind of dances around it, saying he's just tired. But things were fine and normal until I got my shot. I feel like it was a waste of time to get it, and now I have done something unnatural to my body, for no reason. I don't know what to do about this.