thanks for sharing your concern.
According to the history given , it could be gingival irritation
or formation of pocket or sometimes infection in the teeth too.
In many cases the bleeding may be due to overextension of the margins of the crown into the gum. Sometimes there could be sharp margins too. Check for them too.
I would advise you to go for oral prophylaxis first. and this should be followed by replacement of crown. Check for occlusal fittings too. With an articulating paper.
if still, your problem persists then see your dentist
for the clinical examination for any underline cause.
Hope this helps you.