Hey there
I don't have the exact problem as you, but there was a time (that lasted a couple months) where my bf kept trying to get me off the phone with all these little excuses and lies. I just couldn't understand why. I kept thinking he's pushing me away, or doesn't want to be with me at all. I got hurt, very upset, pretty much depressed.
and it was all a misunderstanding altogether. For my fault, he said whenever i call him, i always stay on the phone too long with "silence" of doing nothing and it gets annoying to him that we're sitting on the phone for like 20 minutes doing nothing and he just wants to get off. He told me it's not that he doesn't want to be with me, its just the silence was hella annoying and having that continue over and over.
So for you, maybe yall just need some space and not be together a lot. I'm the type who ALWAYS wants to be wtih my bf. he's my best friend (i can talk makeup, hair, clothes, anything under the sun) and i always go to him, but space is what i should have given him, and maybe you can try that too?
I also whine & nag like there's no tomorrow and i know my bf doesn't like it (cuz it brings the mood down and all) so after talking things out with my bf, i learned that to communicate, you really have to try to word things out right, nicely, and no nagging. Like, eliminate the tone and try to make it sound more "conversational" rather than the "arguing" noise, and I find that helps a lot. To also be open allows the guy not to feel "attacked" or "accused" and he'll feel more comfortable knowing that what he'll say wont' make you explode at him. I had a problem where when he told me something "bad" i'd explode, and from then he always kept things to himself or create a little lie cuz he was scared to tell me cuz i'd yell at him. So now, i'm more calm and now he's more open to me.
Also, he might not be aware of what he's doing! I have a guyfriend whom 2 of my girlfriends told him that he was "being mean" to them and "ignoring" them and such. That guy was doing the same thing to me, and he apologized to all 3 of us girls saying that he really did not realize he was doing all the ignoring and pushing away at all. He had no clue. He also mentioned he was in a man's equivalent of "PMS" XD. But really, guys do have their pms and perhaps your man might be having his pms phase? and btw, my guyfriend's pms stage went on for about 1.5 months @_@ so its not anything short from what i experienced. (but of course each person varies)
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So overall, to try to eliminate his negative thought of you as "nagging" and "selfish", I really suggest you talk with him, but in a different tone. A more conversational friendly tone, even if you have to fake it. Really try to calm urself down because when you're tense, it makes the guy tense too and 1000X worried of when you'll drop a word-bombing of essays at him yelling etc. Even if what he says isn't want you'd like to hear, remember that, no offense, guys aren't good at explaining how they feel. Things come out more blunt and sometimes harsh even though it isn't meant to be like that. THey just aren't good at talking emotions ^^(), so give him a chance, and when you get upset at what he says, try asking him to elaborate more on it to better understand what he meant rather than make assumptions.
Ask him what would he like to see you do that would make him happy and not act the way he's acting and if he's open enough, he should let you know basically the answer how to fix this all up. Since that should work (not all the time though, but its worth a shot), that should take care of the guy's side of the problem.
Sorry i wrote an essay for you but i really wanted to help!