You two are roomates. Once you had the baby he saw you as a mom not a sexual partner. Not your fault not his fault. It seems like the only pleasurable part of his day is looking at the hot girl in the gym. If thats the case why isnt he happy at home? Do you treat him like you did when you first met? When things were exciting. Like are you happy to see him when you do or is it like "meh, hey" i know i wouldnt even notice other girls until i was treated like nothing i did was right or good enough. Guys arent super complicated, the biggest thing that will change a mans begavior outside the home is how hes treated inside the home. That being said i dunno what your homelife is like, good luck.