I have experience that same thing before ... with my period. I am on birth control as well. I have noticed that it cycles for me .. some months are worse then others. One month fine other month really bad. i woke up one morning the day i was getting my period, I began to get really hot .. sweaty and i felt like vomitting.went to the washroom 5 min later and there it was! It has not happened in almost a year now which is good! I do experiece in cycles bad PMs symptoms really bad cramps, sore lower back, headahces, tender inflated sore breasts. Very uncomfortable! If your breasts are very sore tender and appear bigger just before u get your period it is very normal! it may just be hormones before and during a period., It can also be that you were on the pill and went off of it and your hormone levels have changed. hope this helps.. just wanted to let you know i have experienced the nausea just before the period started as well.