First, I'd decrease the frequence to a few times a week, not a day. If that doesn't help, try to switch your mind off it. Mind set is a big part of it. That's what I do when I want to last longer than usual.
I am guessing when you masturbate, you just try to do it really fast and finish right away. What you can try to do is when you're close to the point of no return, stop and let the feeling subside. Then keep repeating for a few times before you finish. Actually unlike you, I have a problem of having delayed ejaculation. With a condom I have a 0% ejaculation rate. Without a condom it's about a 30% chance unless I do not masturbate for 1-2 weeks. My penis will get irritated faster than I ejaculate on most cases. I also masturbate quite frequently and I guess it's because i'm used to a tight grip
For some guys, it's all in their heads. I know a dude that has to 'go elsewhere' in his mind to hold off ejaculation. During intercourse, wearing a condom may help. There are other things you can try and this link has info on that. https://www.mayoclinic.org/diseases-conditions/premature-ejaculation/diagnosis-treatment/drc-20354905
Is the issue having sex with your partners? Believe it or not, masturbating an hour before sex with your partner may actually help you. Strengthening your pelvic floor muscles can help. Instructions on how to do so in that link but you find the pelvic floor muscles by stopping the stream of urine. The ones that do that are the pelvic floor muscles. Basically you then try to contract those muscles when lying down, move on to doing that when standing, sitting, etc. as they get stronger. Do 3 sessions of that a day.
I have a similar problem. I am 28 years old male and I have been doing masturbation from 11-12 years. I have 2 problems in fact. the first one is pretty much the same as you. I ejaculate in less then 30 seconds and some time even before that secondly the strenght and quality of errection has gone down. I am really worried. It affects my confidence a lot. Need help too