Hi Jmix,
One of the hidden side effects of porn is that it trains your brain to respond to virtual sex rather than sex with real women. It will take some time to re-adjust to your new relationship but an easy way to speed this process is to do lots of "bonding-behaviors" which are cuddling, touching, caressing, holding eachother, etc.
This will help to correct the imbalance in the brain and re-adjust your body to being intimate and comfortable with real women.
These activities have been shown to produce a neuro-chemical in the brain called oxytocin, which has been shown to help in getting erections (and help you ease addictions and instead feel good).
Don't worry, it happens to lots of guys and just takes a bit of time and good intimacy and care. Be easy on yourself and have a good time getting to know eachother.
Have you cut out the masturbation as well? Or just the use of porn while you masturbate?
If you're used to the feel of your hand, plus the fact that you can control the pace more effectively on your own, then it make take a little time to re-adjust and re-educate, as RyanRandolph was saying.
Plus, if you haven't had any sort of stimulation for several days before sex with your new woman, you are likely to be able to be aroused more easily.
I did cut it out for almost 2 weeks, and we were fooling around, and it felt nice, and I tend to lose the erection pretty quickly if my mind wonders, and it does that quite often. I don't know what to do, or how to tell my partner about this issue. I was thinking about taking some testosterone pills or something to boost that. Would that be a good idea or what can I do to not think about this when this happens, cuz when it does, I can't stop thinking about how to get it up, and I lose my drive.
I've been there, so I know the frustration - and a lot of the problem arises because you are worrying about losing it, and then the worrying itself causes you to lose it!
I don't have any simple fixes for this, in my case it got better over time and as my confidence re-established. But in my case I had the advantage of an understanding and supportive wife who could help me - not so easy in your position where you are embarking on a new relationship, and it's not so straightforward to ask her to help you past this issue. In fact, the pressure to "perform" with a new partner is also probably a contribution to the issue.
I don't know if this is the case for you, but in my situation I had no problem staying aroused during foreplay, I'd only start to lose it soon after we started vaginal penetration. If this is the case for you, try doing plenty of foreplay stuff so you are really very aroused before you start penetration, then get to orgasm nice and quick. That may not be how you (or indeed she) really want sex to be, but it's better than not reaching orgasm, and it'll help build your confidence so you will be able to go for longer in the future.