Any time you want, as you’re off the pill now you’re adjusting off and side effects like irregular bleeding are common, and going back on the pill will mean you’re back in the 3 month adjustment phase of the pill again and you’re unfortunately likely to experience effects like cramps, irregular bleeding etc anyway during that time. So there’s no way to predict/prevent irregular bleeding. Be aware stopping and restarting the pill when on a combined pill will potentially leave you at a higher risk of blood clots when you restart again. The pill is not meant to be used like that.