spotting???

Fern

For the past 2 days now (yesterday and today) I've been lightly bleeding and then maybe half an hour later there was nothing and then today the same but lightly bleeding for a little longer. I've been getting lower back pain and cramps. yesterday was 12 days since I had sex last and my period isn't due for another week and a half. I've taken a test today but it came back negative......anyone have any ideas because this is a first for me 🙈🙈