My ex and i lost our virginity to each other and whenever we had sex it burned and hurt so bad. why is this?

Many reasons: Can be sore due to lack of lubrication or overly rough technique and unfortunately despite hollywood movies often takes some experience - even if changing to a new partner to work out what is enjoyable and what is painful. May be helpful to use lubrication. There is also the possibility of some treatable medical disorder such as thrush or vulvodynia or even endometriosis suggest see Dr to check