Could you please be more specific? How much lemon and how much olive oil did you take? When? There are so many "flushes" out there.... An when did you take the artichoke? This may have produced more bile flow, perhaps causing feeling of pressure?
I am only familiar with the the one where you take 1 TBs of olive oil mixed with lemon juice and glass of water, on empty stomach. I did this for quite a while, 1/2 hour before breakfast, no problems, a nice cleanse.