First of all, you will do weird things when you're high. And there is nothing 'wrong' with masturbating to asian porn, you could be doing much worse! This isn't really a sexual problem, it's a drug addiction problem.

However, since this is affecting your life and you don't like it, you struggle with it, I would go to a doc of some sort to help you get off meth. Or a meth support group or rehab center. It sounds like you've done a good job so far, but it's a really tough struggle and you deserve to have some help! Poke around in your phone book for support groups or addiction specialists/therapists, rehab, whatever you find.

The meth with keep controlling you until you find a way to get rid of it. And really, it's hard and you will need help, or at least a group of people who have been through it and can help encourage you through it.

First off, you're asking us what a professional doctor's opinion might be when you yourself could be seeing a professional doctor (or maybe you have transportation issues or embarrassment issues). If its embarrassment issues I think you should still go since I went to my school counsellor to resolve personal problems thinking I was going to embarrass myself and do the dumbest thing ever but I ended up getting the emotional help I needed to be fully functional. I think doing activities that may add structure to your life may help. The following is a list of activities that may be helpful (I tried to include as many activities allowing you to cannot to other people since other people can help you in ways we couldn't imagine):
1. Martial arts-Usually a scam but maybe you can find a good teacher and add purpose to your life
2. Lifting weights-There's plenty of people to meet in the gym and being strong is one thing that can help a male feel more confidence about himself (at least it worked that way for me)
3. Jogging-Kind of a solitary sport, but great for fitness and can give you something to work at. Main advantage is being a sport that requires little extra equipment (just maybe watch and decent shoes)
4. Work at McDonalds (or similar job)-I'm not sure if you have a job or not. If you do, ignore this. But if you don't, getting a job can not only give you money but can add purpose and structure to your life
5. Join an adults' soccer club or something, you can meet lots of people and soccer is also a fun game

I'd say its somewhat normal... I've masturbated tweaked out on Ritalin/Concerta before, as well as Amphetamine... And weed MANY times lol.

Speedy drugs can make you extremely horny and i've never tried meth but i'm guessing its like coke x 10. I'm guessing it kind of makes you fantasize and make the experience feel "real" while masturbating and enhances it very well, which is why you do it.

I can understand what you're going through... The problem is, you're going to become dependent on meth to control your sex-drive, which is just going to cause a lot of long-term problems.