Sex before lp. lp was heavy..guess due to bc pill change. nauseated, back pain, watery white discharge, headaches, eating more, tired, swollen breasts?

Probably the pill: Read through that package insert again. I think you will find all your symptoms as side effects, i would stop the pill and see if your body normalizes.

Pill change?: It sounds like you just changed to a different bcp, and had a heavier period, plus nausea, headaches, tiredness. If you didn't miss any pills it is unlikely you are pregnant - if you did miss pills check a pregnancy test! it could be the different bcp are causing some of what you are noticing.