Committment issues?

Ok so I’ve been wrestling with this for quite a while and im turning the issue over to you. Im in a semi serious relationship thats also long distance. I say semi serious because right now it seems very one sided. We are engaged and im currently in the process of saving to relocate to where hes at. My issue is the fact that he doesnt appear to be as serious about this as I thought he was. Maybe im just reading to much into things and over analysing, but the thing is how can I even broach the subject with someone who doesnt appear to ever have time for me?relationships are for the most part a partnership, but hes only around when its convenient for him. If he has a bad day or if he needs to talk its pretty much the only time I hear from him. I feel so cut off that even when I do get the opportunity to discuss how I feel I dont even want to try to explain because he has major time constraints and it seems pointless to try and get into something if I know hes going to bail in 5 minutes. Everyone keeps telling me “he has a life” but I think its a lot deeper than that. Im worried that im something of a um… Bypass? (is that a good word?) for him. Like hes maybe using me to get past this particular point in his life. It seems like everything in his life takes precedence over me. Im not quite sure how to deal. He had me head over heels from the moment I spoke to him. All he has to do is smile and I forget everything.I treat him extremely well, I dont play mind games, and im very very honest with him. If we have issues instead of fighting I try to communicate. The thing is, over the last few months things have been going steadily downhill for me and I need a little more support from him than I’ve been getting and when I try to explain this to him I have this feeling that hes somehow going to see it as nagging or complaining so I just let it fester inside me until I want to explode. Aside from the fact that I cant really express how I feel theres a lot of other issues to this. I mentioned time constraints, this means that I get to talk to him once every 3 days or so for less than an hr. On the off chance that he shows up early he always bails before I can get into any sort of serious discussion with him. I never know where he is, but he expects me to wait around for him 24/7. The days he says I’ll see him he doesnt show, or he shows when he knows I cant see him at all. The more time that goes by the more I see how selfish and disrespectful he is. I do love him and im committed to trying to find a solution here or I wouldnt be posting about it, but I need other perspectives on this matter.