1] cock rings are a little _too_ dangerous if not correctly used. If you place them before u get errect, then get hard, it means you pump alot of blood in your cock, that cannot go away. Also it will become very difficult to remove the cock-ring. The happiest-end , you get a blueish sore cock, and you do NOT want to know the worst end.
PS: all this assumed you were a beginner, with a mis-sized ring

2] the 'pain' part isn't always good, for some it can make them cum right away (painlovers), while others (like me) with ZERO pain tollerance, will stay away from you for as long as they live.
If you do not like pain it is really HORRIBLE to feel something like that when you're most vulnerable. [and yes, this is a man's point of view]

3] a nice way would be to take a break, and the guy does some oral to the girl for a change. (NOT a 69).

and also... if you don't have that really bad DOWN MOOD after cumming, you could just cum !

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TmS