WHAT DO YOU THINK??? WHY IS HE ACTING THIS WAY?

my boyfriend just turned 25 yesterday, we've been together for 2 yrs. I told him i wanted to take him to sea world, get him a shirt and such. i tol him this a week before his bday and hes like no no you dont make alot of money, its ok. but i told him no i want to. something happned to where i ran into an unexpected small financial dillema and it left me with $10-$15 to spend on him. i did what i COULD do and wanted, i made him a giant card, decorating it & writing a story length on how i feel about him, also made him a giant cookie cake heart that was hard to make. i told him to meet me at the mall i have 3 $10 shirts picked out that i knew he would like from his fav. company. he liked them but ended up not wanting them..later on we got ino a HUGE argument of how he always got me gifts for my bday, bought dinners/movie tickets, and i couldnt even get him a gift, he said i was a lowsy gf and i didnt do muchto show him icare and love him. why is he acting this way, i was finacially unexpectably stuck????