HOW DO I GIVE MY BF THE RIGHT ********?!!??! PLEASE HELP!!!!?

so last night my boyfriend and I were making out and I proceeded to give him a but my hand gave out before i could make him finish and he guided me A LOT and he cued me to go faster and everything but I had no energy left in me to finish him everytime...like we would come super close and then my arm would give out!!! We went at it for a good half hour and I just couldn't. I felt absolutely terrible after but he kept telling me that he loves me so much and that this does not mean **** to him and he knows I'm trying and since its the first time I've ever tried it I should really not feel bad and that we'll get it right soon enough and even if we don't he doesn't care he just loves me for who I am and that I'm soooo perfect and that if it doesn't bother him it shouldn't bother me. he was being superrrrr kind about the entire thing BUT can someone please tell me HOW i can get him off w/out stopping!?!!? Btw we are both 19 but I've never given a guy a hand job just cuz i was totally against that stuff until I met him...we have been together for 4 months and we love eachother to death and I wnat to be able to do this for him! pLEASE HELPP!!