Hi I had been on depo injection and hadnt had period for 2 years or more then decided to try cilest pill been on them since jan 25th 2013 anyway on wed 27th march I had unprotected sex with my partner and maybe a little rough bled after not period just bleeding on sun 31st I experienced nausea and headache snd since then dizziness nausea cramps and back ache today fri 5th april nausea has stopped but backache really bad cramp pain especially left hand side bigger than normal stomach need to pee more frequent and tonight light pinkish brown spotting on my underwear what can it be?