few things i wanna point out here...

1. Unwanted Pregnancy - Even if u do get to hv all the thrusting action, due to his "ability" to cum fast, he might actually come inside u by accident and causing u pregnant...ever thought of doing foreplay then fingering u till u cum instead? (dun ask how. got minor here. go google urself)

2. what kind of doctor is he seeking? Premature ejaculation can be caused by several factors, which is divided into two:

-health issue - unfit physically, lack of control, lack of stamina, etc...
-mental/ psychology issue- low self esteem , performance issue, stress, etc...

3. understand that a lot breakups are caused by this issue also, we all know u are stressed due to this, but if possible dun stress the guy or blame him. it will eventually make matters worse. Guys who hv this issue will eventually hv lacking self confidence.

if u truly love him and would like to continue on with this relationship, pls be patient as this will take some time to recover. using tongkat ali /etc medicine may work, but long time consumption will leave side effects for sure...nothing can beat doing it the natural way.

-just my 2 cents.