Want to be sexy to him.

I have been with my bf for four and a half years now. He seems to have lost interest. I have gained some happy weight but I don’t think I look bad. And so did he. But he still turns me on. I want to turn him on. He has been denying me lately and I want to be irresistible to him. We are having less sex and he’s watching porn a little bit. I almost want to ask him if I am still. But where’s the sexiness in asking him that. That just looks pathetic. I want to do something to basically awaken him again. Any advice?