Good questions. Don't confuse mental and emotional. You are supposed to be getting out of the mind and into feelings
Both body sensations / body ailments in general and emotional feelings are assumed to caused by suppressed negative psychic energy. If body sensations are dominating your meditative experience, it's not a problem. Let them become your focus point and take them through the process. Stay with them for as long as necessary - minutes, days, or months. Body sensations are a completely valid pathway to subconscious holdings. Eventually you will be led to the corresponding emotional feelings, and then you include them in your process. Go with whatever is most dominant - body or emotional, they both lead to clearing the suppressed psychic negativity.
You don't necessarily need to push back to historical memory of how things originated. In theory, the past is projected upon and reflected by the present, and working with present manifestations in body or feelings will release the past. In practice, however, if past memories spontaneously jump up as you are processing present experience, you should include them in your process, just as you would a present-day event. See them as if they are happening now. They have particular significance for you and can lead to helpful past life recall, if that's what you need. Let yourself be guided by your unconscious higher self. Just remember that when you go into a recall, whether it's childhood or "past" life, to apply all the steps of the process to that scenario. For example, make sure you are taking responsibility for the recall experience and not falling into blame.