Inexperienced bf (cums fast/doesn’t stay hard)

So I’m 20, my bf is 22. We recently started dating. I’m pretty experienced sexually and was in a 3 year relationship. He on the other hand was a complete Virgin. Had gotten a blow job once in his life before me but never came. We recently began to have sex.. only thing that sucks is when we do he either 1.) cums extremely fast OR 2.) goes completely soft if we stop for even a second.

He says that’s it’s because he’s nervous he isn’t pleasing me, he’s worried about cumming too fast, and he’s scared of getting me pregnant (even though I have an IUD)... I’ve tried to reassure him several times on all of these things but nothing seems to help. He doesn’t really know what he’s doing even though I try to teach him, and I know I shouldn’t take him personal but when he goes soft I always feel like it’s my fault and that I’m gross.

What do you think is going on and how do we fix this? I just wanna be able to have good sex with him :/

Could he have erectile dysfunction?