Day of your sex; i.e. about two weeks prior to the period falls near the day of egg release. So the chances of you being pregnant are very high.
If the spotting was two weeks before the menses, it likely to happen at the time of egg release. However, such bleeding continuing and becoming heavier is rather uncommon and does not fit into the normalcy. I would advice to get thorough check up from gynae and ultrasonography
Unfortunately, you have not mentioned your age. This type of the bleeding then could be put under post-coital bleeding; i.e. bleeding after the intercourse. However, this will have more weightage around menopausal age, though at any time it cannot be ignored.
Somehow, from the description this appears to be the bleeding due to hormonal
imbalance than anything else. Please get your gynae consultants opinion on this after clinical examination.