19 yr old w/ erectile dysfunction- Please Help!

Im 19 years old I consume alcohol in excessive amounts I used to smoke cigarretes but not any more, now that I have a new girl friend I eat fast food most of the time. Before all of this I used to be in great shape, didnt consume any alcohol or smoke either, I ate fruits and healthy meals. My last girlfriend used to always compliment me on my really hard erections and the size of my penis. Every time we had intercourse she was swept off her feet with my performance. It was never a problem to me to get an erection. But recently I've been having problems with my penis being erect and it doesnt get as big as it was before. My girlfriend is very attractive and I love making love to her
we've been doing it everyday for the last three weeks and somedays more than one time per day(might be this a contributing factor for my problem?) also I would like to point out that our intercourses are not your typical missionary slow sex, ours is rough and hard for a minimum time of 30 mins which I do enjoy but its emotionally tiring me because it gets in my thoughts that maybe shes with me just for the sex and the day that im unable to satisfy her as I currently do, she will leave me
I also have a past of cocaine abuse but that is over( is there a permanent damage for this) I admit that it did "slow" me down  because before I started consuming I used to be a straight A student and I would be very good at critical thinking and decision making but now its a different story
When I used to be single I used to observe an immense quantity of pornography and used to masturbate 3 times a day( can this cause a psychological or nerve problem) and while this might sound typical for a guy my age, it is not because I would be extremely picky with the women I would masturbate to, they needed to be perfect in every sense and I mostly watched oral sex because intercourse wouldnt arouse me
without further ado what i would really like to know is if this might be a circulatory problem because of all the fat and alcohol that I consume or this is just a psychological issue?

ps: now and then I watch a little bit of pornography and im able to get a perfect erection close to the ones I used to obtain

[SixStringer]

You have several issues going on here at first glance.   From the health standpoint, it would be great if you could go back to eating better with whole grains, vegetables, fruits, and so on, and as you have written, things were better then.  Keep off the tobacco and cocaine.  You may still be experiencing some effects from them, but as time goes on you will overcome this.  As far as the sex goes, try to get away from the situation being a "performance".  Of course, everyone is different, but more than once per day and 30 minute sessions seems too much and will affect your organs as you have noticed.  You need to have some restorative time.  Devote some time to other forms of exercise with or without your girlfriend.  Don't overdue things so that they become marathons and expose you to burnouts and boredom.  Quite often, going without something for at least a short time builds the tension so when "it happens" it kicks in the old enthusiasm of old.  You are young and can make the necessary changes that is best for your situation.