Hello ykk,
I'm experiencing those "symptoms" and some more (problems with digesting, diarrhea, stomach pain, intestinal cramps) too. They started about three month ago and are much better now. It first started with real weird energy movements in my stomach/solar plexus area. After that I started getting diarrhea, which set in often directly after meditation. Since than I became quite sensitive to all sorts of food and therefore I changed my eating habits completely. Note: I didn't force myself to stop eating meat, milk, etc. it happend by itself, because it seemed like i stopped harming myself by eating too much and the "wrong" food.
I also went to an internist to get my stomach and gastrointestinal tract checked and everything was ok. Maybe you can do that too, just to be sure everything is ok on a medical point of view.
My meditation teacher, which I talk to once a week says, that this has something todo with the stage I'm in at the moment. I'm practicing mindful prostration/walking/sitting meditation (Ajaan Tong Sirimangalo tradition). I deal with those things in observing them, as I do it with all other phenomena that comes up. Feeling, feeling, feeling, disliking, disliking disliking, pain, pain pain, tension tension tension. Thinking, thinking, thinking, worries, worries, worries, etc. I just observe what is present in this moment, sometimes those things are present, most of the time they are not.
May I ask some questions?
Have you changed something about your eating habits, since you rercognized your symptoms? If yes, does it make any difference? My meditation teacher says (as mentioned above) it mostly has something to do with the stage I'm in, but I don't get diarrhea etc. as often as before, since I started changing my eating habits. Now I get diarrhea sometimes after meditation, but it's not very often (probably 1 every two weeks)
Why are you mixing techniques? Are you getting bored of only one? Do you doubt your practice-method? There you probably have something to observe.
Do you have the feeling, that meditation is something, which is fun and kind of light, even in times when it is the opposit or is it exhausting and forced? Is your "view" open to let things in, or too focused, tight and narrow?
What is your aim of meditation? Reaching desireable states of equanimity and powerful mind-states? Are states like "dullness, boredom, anger, frustration, guilt, etc." are not of your interest?
I'm asking you this (maybe provocative) questions, because they where helpful asking them to myself. If they confuse you, I'm sorry:)
I'm also sorry if my english is confusing you ;-). It's not my foreign language, but I guess you already know that.
Greetings, Georg