I used to have this problem until recently.
Once I started banging multiple women at least one time a day I could easily go 20 minutes plus easily without cumming except once I start lasting so long I run into a new problem. The girl couldn't stay wet for long enough so I had to start using lube more often in the later rounds.
Before I was banging multiple women I would masterbate every morning and by the time evening came around when I would fuck a girl having already masterbated that morning help me last much longer.
Once I started banging multiple women at least one time a day I could easily go 20 minutes plus easily without cumming except once I start lasting so long I run into a new problem. The girl couldn't stay wet for long enough so I had to start using lube more often in the later rounds.
Before I was banging multiple women I would masterbate every morning and by the time evening came around when I would fuck a girl having already masterbated that morning help me last much longer.