Periods related. Affected by altitude) ?

Hi, I went on a high altitude Himalayan trek in uttarakhand 12000 feet on 20th March to 25th march. My periods were on 22nd March to 25th March. Post that, I did another trek 11000 feet on 2nd - 3rd April. I had unprotected sex on 27th March night, had an Unwanted 72 pill on 29th March night (does it work under 72 hours?) I had periods or spotting of 2 days 5th April to 6th April. Do I have chances of being pregnant? When is my next cycle due? Please answer, I am very worried. I do not want pregnancy, how should I avoid now (any food recommendation)? I otherwise have a healthy period cycle, now it is all messed up. Is it due to this pill or the trek (I have heard that periods are affected by altitude)? Thanks, Sushmita