I have been slain in the Spirit, and I have also experienced what OP describes during Mass. The first was while I was actually in a group praying for release of the charisms of the Holy Spirit and praying to Him specifically to work in my life and to surrender my will to His. The second was typical low blood sugar episode I have learned to recognize as I learn more about my diabetes. I suggest focusing on possible physical causes first, perhaps paying attention to what has been going on with you–food, sleep, meds, other influences–before you assume there is a spiritual thing happening. Continue doing what you are doing, namely report odd symptoms to your doctor. If you are really being “slain in the Spirit” or you are attending the type of worship where this is an expected event you should always be accompanied by someone trained to assist people when it happens, to make sure they don’t fall, hit their head etc…
I don’t think, this is my opinion, that there is any room on this forum for anyone to bash the spirituality of another, particularly a spiritual expression that has been endorsed by the Church, simply because one is not accustomed to it or comfortable with it.