im really having a hard time with my boyfriends mood swings. its nothing new he's always had them but now its becoming a major irritation and he's so childish i don't know what to think or do. so for eample his mood swings happen when things don't go his way and he looks to me to take his frustraion out and its up to me to fix the problem. im going to go into detail. here is one such example, please keep in mind this kind of thing happens all the time with different scenarios.
bf says he needs to use my printer, no big deal, begins to freak out throwing a childs temper tantrum because the printer will not print for some unknown reason, gets fed up starts cussing me out about how dumb my printer is and why isn't it working and how this is stupid and i need to fix it....i walk into the room push the printer on switch wait a second and it begins printing his papers....all that tantrum because he didn't turn the button on correctly first :/ no apology or thanks just goes about like nothing happened.
another example: " babe i can't find ( insert item) this is F****** stupid, i hate everything why can't i find this, will you get off you ***** and help me find it..tons of other yelling .....its in his pocket or in plan view....hands it to him....oh there it is.... like nothing happened

i deal with these childish tantrums all the time from him...he's thirty years old....why is he acting this childish when things don't go his way, and places blame and the solution on me?

a little side note for humor: he says he doesn't want to grow up and have the pressures of an adult life such as having kids and such which i agree with, and he wants to remain young spirited ( no problem)....but i did not sign up to take care of an adult who completely acts and behaves worse than a three year old with tantrums and things not going their way. so what is the psycological issue going on here