Delayed Ejaculation

Hey guys, first time poster here looking for advice.

I have been watching porn and masturbating to it for around a decade, since my early teens. I have in the past year lost my virginity and in the past six months established myself with a girlfriend. The problem I have is that I find it very difficult to ejaculate during intercourse. At first I put this problem down to being drunk, as my initial experiences were with one night stands. However, the problem has persisted when I have have sober sex with my loving girlfriend. I am sure that this problem is porn related so I am determined to quit viewing porn and masturbating all together. I'm wondering if anybody out there has had a similar experience and if I can expect my problems with delayed ejaculation to clear up once I quit with the porn?

Thank you all very much for your help!