Thanks for writing to us with your health concern.
The fact is simple - pregnancy
cannot result from anal sex.
IT is not normal to bleed after a period.
There could be various reasons such as stress, anxiety, weight gain, hormonal
imbalance, late nights, binge eating
COnsult a gynaecologist and go for formal evaluation - internal exam ( per speculum and per vaginum ) plus pelvic ultrasound
scan and hormonal levels.
All the best
Please feel free to discuss further.