What do i dooooo?

i recently lost my V to my boyfriend earlier in the year. we didn’t exactly finish either... okay so the past few times we’ve gotten the opportunity to have sex once id get on top he’d lose his erection. and once it goes down it doesnt stop or come back... he told me it feels great and everything and i trust him on his word. is there maybe something i did wrong or maybe i could do to make sure he stays high and mighty? im pretty sure its just cuz he’s scared and nervous 😂