If you felt groggy, etc., after eating meat again, it could just simply be the fact that your body is used to breaking down plant food, which, in many if not all cases, is a lot easier on the body.
However, it sounds like you don't have any ethical feelings against meat, so it sounds like you can make a choice that just leaves you happy. I believe you can be healthy eating vegan, raw, veggie and omnivorous. I think being happy about your diet is the most important factor.
