Ejeculation problem. Can cure it.

I am doing masterbation almost 5-6 times a week since my teen age and now when am 28 facing ejeculation issues. In last few years i had intercourse with so many girls, but I dont feel any sensation during vegial intercourse . But I am pretty good with Handjob from partners and masterbation by own but not veginal intercourse. i am also overweight so cannot pump too much like any other normal person. So it this problem is due to over masterbation or any other medical issue. Or its like am very used to of masterbation only. I read that if I stop masterbation then this problem can be cured but its very difficult for me to hold for 1 month or so..I am very frustrated now because of this. Do I need to meet any sexologist or just stopping the masterbation can cure it.