My breath smells, I do not eat junk food. When I get up in the morning I find small quantity of blood in spit. Why is it so?

Perio issues ? You most likely have neglected your teeth and gums and have some form of periodontal (gum) disease. You may also have cavities. When was your last dental checkup and cleaning? See your dentist to be evaluated.
Grinding? You may grind your teeth in your sleep. Schedule with your dentist for examining areas of food impaction, faulty restoration, abscesses, open contacts, plunging cusps, etc... Must locate and eliminate the causes of gingival inflammation.
Bad smell. It is ussually due to gingivitis, so have a dentist look your gum and clean it for you.