Me and my husband haven't had sex in 4 months

I have no idea what my husband's deal is. For 4 months every time I ask to have sex he says no. He says he's not in the mood ever. I'm honestly just about to buy a toy but I feel a toy can only do so much. I'm horny all the time constantly and we have little not been having sex at all. I put on something sexy and tried to get him in the mood but he tells me to stop and he's not in the mood. He started antidepressants back in May so could that be it? And if it is would it make me horrible to ask him to change them?