Thank you for asking your query.
The first option - that you had sex and got pregnant again is not likely, as the uterus needs time to 'rebuild' after a pregnancy.
The second option - twins and one among the twins surviving is theoretical possibility. But the odds are very less in real life.
So most probably this could have been an incomplete abortion (from the first time). This can cause pregnancy symptoms and bleeding. This can be confirmed with a simple USG scan. You can discuss this with your Doctor and get the scan done to confirm it.
Hope this helps.
Patient replied :
So is it impossible that I am pregnant? What are the chances?
No, its not impossible. You will need a Ultrasound scan to tell that.