I do not think your sleeping habit is a contributory factor to the bruises. Even if it does, it should not affect significantly.
There seems to be a more serious concern here.
You may be suffering from a bout of viral fever
now. In this, the platelet counts drop and you tend to have bruises in the skin and on the joints.
You should get your complete blood count
done including Platelet count.
Meanwhile, take adequate bed rest
. Drink plenty of fluids.
You should be fine soon.