Sounds like good advice above; I've never suffered from PE so I'm not in a position to add much to that. It may be possible to by creams that reduce your sensitivity so help you last longer, although I've no idea how effective they really are - try a website specialising in sex toys etc.
Frequent masturbation (or for that matter sex) will reduce the amount of semen in each ejaculation, yes. But that's simply because you are emptying the tanks before they've had much chance to re-fill - leave it for 2 or 3 days and you will straight away have more semen. Not sure whether it really reduces sexuality; I guess if you haven't done anything for 2 or 3 days you are more likely to be desperate for it than if you had sex or masturbation a few hours earlier, but I doubt there is a long-term effect. Shouldn't make any difference to your fertility, i.e. ability to make a girl pregnant.
There's plenty of books full of advice (and videos that are specifically instructional, rather than just porn). I guess the classic text is "The Joy of Sex"; it's been around a fair few years, but sex is still sex and the advice is still sound. Just go to Amazon, they have a specific section on sex advice books (under Books > Health, Family & Lifestyle > Sex, at least on the UK site), have a browse and see what appeals to you.
Hi, it is normal - I used to have the same problem when I started my sex life with girls. What helped me:
-do not stop sexual activities after your first ejaculation, you can play with your girl, touch her, perform oral sex on her, caress her etc...she can also touch you in your private parts or where it feels good and then after some time if you get aroused again, you can have sex again. Ejaculation does not have to mean the end of sex, feel free to go on and try to explain this to your girlfriend. The second or next intercourse can last a little bit longer.
-it would be helpful if she could bring you to orgasm as often as possible. If you build up a lot of tension and then there is a rare opportunity for sex, it is just natural that your body reacts in this quick way. My problems disappeared only after some time of regular and frequent sex (before that I used to ejaculate sometimes also before I got undressed:). Now I am 33 years and everything is OK, it just needs a lot of regular and frequent sexual contacts (in my case it was the only effective remedy).
-or first your girlfriend can bring you to orgasm by her hand (or oral), then you can enjoy some sexual plays again and the next erection(s) should last longer.
-a little help can be provided also by condoms - they make penis less sensitive to stimulation and sometimes you can last a little bit longer because of this with a condom.
Just don´t panic, it is normal and it should get better.
As for her satisfaction, I recommend to satisfy her by some non-coital activities, you can use manual or oral stimilation of her clitoris / vagina after (or before) the intercourse and she can "teach" you how to bring her to orgasms in this way.
As for books, I am not British or American, so I don´t know books popular in those countries, but I can recommend you one website: netdoctor.co.uk, there is a section Sex and relationships etc...they have some articles about sexuality or you can search something on the internet in google, there are many sites with useful information (but again, do not believe in everything you find there).
All the best,
severin76