Here is an article I wrote regarding EFT, http://thechristianmeditator.com/should-christians-practice-eft-or-avoid-it/
To answer your question, could things get worse before they get better, I would say possibly.
EFT requires us to look within for our fears and limiting beliefs and bring them out into the open. This can be a scary thing. Often we think that acknowledging that we are afraid, upset, or angry is wrong so we try to deny or bury these feelings. Yet, just because we don’t admit them, doesn’t mean they don’t exist. They are just keep living in our subsconscious mind having the same detrimental affects on us.
Once we let these beliefs and feelings come up and out it can trigger a whole lot of different emotions and one or two sessions of eft are probably not enough to permanent freedom. Remember, we’ve been living with this stuff for usually years.
Once we acknowledge our authentic beliefs (called making friends with the problem), we then begin to use God’s word in the form of positive affirmations to dissolve these mindsets and plant new positive ones. Although you may find some relief, most likely you will need to keep with it for awhile in order to change your subconscious mental patterns. Therefore, keep with it several times a day.
If you are finding emotional baggage that you just can’t cope with on your own, it may be beneficial to talk with a counselor or seek outside help. I hope I answered your question.