Remember that you are eating far less than you normally would so you will have far fewer bm than before. Also as you are still on the liquid stage there is very little 'waste' for your body to get rid of. Follow the instructions from your team and you should be fine. As for periods, I think we all had one after surgery wither it was due or not, as it messes with your hormones, it should settle down after a few months, fingers crossed. Good luck with your journey