When did you start having bruises? And, are they sensitive on touch? Did they hurt?
The most common reason for bruising without visible cause (apart from platelet problems and clotting factor that you ruled out) is
that you are taking some medication that alter your immune system which reflects on your skin as bruises. Also, some natural supplements can be causing this state, such as ginger, garlic, fish oil, etc. because they have blood thinning properties.
It is important that you visit doctor so he/she can do a complete blood count, because easy/unexplained bruising is somewhat serious issue.
I hope it's easily treated. Report back what your doctor said to you. Cheers!
My doctor is weaning me off of my medications to see if that helps.