I've been with my boyfriend now for over a year and having repeated unprotected sex which he ejaculates in me and I'm on the contraceptive injection and been on it over a year now and I've never had a period whilst I've been on it, for the past few days I've been experiencing mild period pains and eating more than I normally do, but today I went to the toilet and noticed a dark red big bubble thing come out ? What could this be ?!?!?!!?