Advice Please!

My SO and I have been together for almost 3 years and are both in our early 20s and I want sex almost every day however he doesn't. He says that he is tired because of work. He works 10 hour shift do manual labor so I know he is but still! I feel like I need to have sex. I'm not very comfortable going solo but I do sometimes. I get rejected almost very time I offer. He says I just have bad timing. I don't know. We used to have sex every day if not twice! Now it's every few weeks. I feel like I need more. We've talked about it before but it just makes him feel bad. I don't know what to do! Almost everything else is going great and we are going to be married soon.