Crazy problem help

Gina
Hiya ladies. 
Last Monday I had 2 positive pregnancy tests. 
Then started clexane injections Tuesday as I have clotting disorder. 
On Friday I started bleeding without pain I went to a&e and they checked viginally and said everything looked as it should and are doing me a scan on Thursday to check baby is ok from inside. 
However today I've just don't a pregnancy test and it's come back negative. What on earth is going on??
Still feel nauseous and off but I feel like I've lost the baby now and can't understand how xx