How do I get that love back?

My fiance & I have been struggling since I've had my son. We've had more issues now than we ever have & I just dont know why. He works days, I work nights so I figure that's part of the problem but he always tells me he feels like I don't feel the same about him. I really dont know if it's because I'm so busy being a mom I forget how to be a lover.. I just really don't know. I feel like if things keep going the way they are, we won't be together much longer & I really don't want that. Is this something normal that happens? Is there anything I can do to make him feel a little more loved? I try everything I can but it all comes back to the same thing. We aren't very intimate because sex hurts me a lot & were both always so tired after work. I've been meaning to get lube, so I need to work on getting that. Does anyone have any other suggestions? Has anyone else went through this with their so after having a baby? Please help, he is my world & I can't stand the thought of losing him..