boyfriend --rejected

me n my boyfriend have been together for 4 months we have developed very strong feelings for each other and we have started saying i love you..but now out of no were he cant nutt wit me or at least its only happened once.. last nite! i didnt kno really wut it was or wut was wrong jus things felt diffrent like mentally may-b. i had no problem (deliver-ing) twice for me... but nuthing for him he sed he felt it  it was like there but nuthing happened??i kno i could have went longer may-b but usually hes happy wit like 30 min or 45 mins....i just felt over whelmed with discourgment. ive never had this problem..im not lose only had 3 partners..im 19 and hes 21 and hes alwayz told me that the sex we have is the best hes ever had in his hole life..like he didnt kno it could b this good. so is there somethin goin on in his HEAD that i dont kno about.somethin he cant get over..is it somethin to do with me or his self im so confused..and i need some advice..i couldnt stay wit sum one if i cant make em do tha deed...do u kno that very alkward ness wen u get off of em with a diff. look on ur face...so any help any one i think its to early in the relationship to go to some sex theripy???or wutever sryy. for the mis spelled...