Is it me? Or is he really just tired?

My boyfriend and I have lived together for almost 7 months now. When I first moved in, I would walk around in a t-shirt and my little boy shorts undies. He use to love it. He would check my *** out every time I got up. Now, it's like nothing to him. Unless I'm bent over and my butt is in the air, then he'll acknowledge it. Six months ago, we made love every single day. At least twice a day. And now, it's about 4 or 5 times a week. Sometimes not even that. Can that really be normal after just 7 months? Our sex life use to be great. Now, it's lazy. We do the same 3 positions, always on the bed, and once he gets off, we're done. He doesn't make sure I'm satisfied. He hardly ever goes down on me anymore. And 9 times out of 10, he says no when I ask for sex. But every single time I leave for work, he watches porn. So then, when I come home horny, he doesn't want to have sex. He says it's because he's tired. He works in construction, so it takes a lot of physical strength. (I've seen. I go to work with him sometimes. It looks like it sucks.) Anyway, I feel like I'm doing something wrong? It's like he's just not into me like he use to be. I can't help but to feel like less of a woman. Everything else about us is great. We get along so good, we're always laughing and having a good time. We hardly ever argue and we love being at home together. But our sex life has sunk. What do I do?!