Help! Im so confused!..

so me and my boyfriend have been together 2 months shy of a year. We've had sex.. or i should say attempted to have sex about 5 or 6 times. Our relationship doesn't run on it and I love that!! My only worry is when it starts to happen he just deflates (if you get what i mean). Our first time I couldn't get him up, he ejaculated trying to do it himself (its a joke to us now). I can get him up without his help now but when he goes to put on his condom he falls. And last night he stayed up but deflated as soon as there was penetration.. I feel like maybe I'm the problem? Or maybe its the condom..? He was a virgin before me so i blamed that but now idk. He feels bad after sex because we couldn't go fully. I tell him its okay because really it is to me. i would say lets just have sex without a condom but hes leaving for military in 3 months and doesnt want me pregnant while hes gone, he wants to be here for it all. Has anyone else had this happen? Is it still happening? I dont know what to do..