If you can get aroused and hard from porn or other things, then it means your kkj still works on the fundamental level.
However in bed if you cant get hard with another woman simply means your kkj is picky.
Either that or you are too nervous or anxious (happens to me a lot
).
I get nervous especially with pretty girls lol but just HJ yourself until you get hard and then proceed.
If you notice, in JAVs also a lot of the male actors go soft so they just HJ themselves until they're hard and they can go at it again.
Other than that, like other folks here have said, supplements that boost nitric oxide (NO) like pine bark extract citrulline will help boost your hardness and ability to stay hard.
Tongkat ali blends will also help getting aroused.
If you really got problem with hardness (i.e. ED), then get a prescription for tadalafil, which also helps boost general blood flow via nitric oxide.
P.S. Also, if you fap to porn a lot, stop that and dont fap to porn anymore (or do it less), instead only fap using just a fleshlight or similar - the idea is to resensitize your brain to get aroused (and orgasm) using just your senses from your little buddy down there. If you're desensitized, you'll probably not even be able to get hard using a fleshlight or your own hands anymore without any visual stimulation, which is all the more reason to cut that shit and use only your dick and a fleshlight to orgasm.