hiii dear
premature ejaculation means before u wish it to ejaculate,, it can be occur with all that have u mentioned
it is not a serious that u think
it is treatable and modifiable
there is no defination of duration of intercourse or ejaculation
it can measure in term of satisfaction but not a term in duration
so satisfaction of both the partner is the main parameter
more excitement can cause premature ejaculation
u can modify it by
using condoms
condoms with lignocaine jelly
change in position like women on top
masturbation before sex also increase your time
stop and start method ( thought diversion) method is very helpful
plz read google
by time you will learn how to do and how to stay a long but understanding between partners is essential
get well soon