from my exp., maybe you are very nervious, or tension about your job or sth else, you can observe
1.how much 'blood' each time, (too much for 2 times should go to doctor)
2. will it persist in next mth
3. any serious plain in tummy when m comes
4. Relax yrself
or else , go to doctor for total check-up for safe
Bless you