hi and welcome,
Since you are using dentures since a long time now , bleeding from the roof of mouth can be due to trauma to the palatal mucosa caused by sharp edges of the denture border or any sharp high points on the inner surface of denture that has hurt the mucosa causing bleeding.
Other possibility can be tight fitting denture that leads to accumulation of saliva and invites fungal and bacterial growth.
i would suggest you to consult your dentist and get the examination done, if there is problem with the denture , the sharp margins can be trimmed off maintaining harmony with oral tissue.
i hope this helps,
take care

dear friend,
thanx, for sharing your concern,

bleeding from the roof of the mouth (palate) could be due to mechanical injury to the underlying tissues.

your history shows that , you are a denture wearer since long time.

so i am sure your denture are well fitting, to the tissues ?

if not it requires to be examined .

you have mentioned that it bleeds when you remove the dentures and try to suck .

this could be due to the pressure developed on sucking on the weak or inflamed palatal tissues .

for this i would suggest you to get clinically evaluated by dentist, also take an xray to see if there is some pathology underneath .

have you checked for any sharp edges in your dentures?

also some times ill fitting dentures lead to accumulation of saliva and fungal and bacterial growth
these could be the pre disposing factors in your case .

get your self clinically examined once .

always store dentures in water when not in use .

regular cleaning them is also mandatory.

gum massage and warm saline rinse might help in your case.
thanx