I'm a 40 yr old I had a supracervical hysterectomy 2 yrs ago. Now having vag. Bleeding monthly. Pap showed endometrial cells on cervix?

Yes. Sometimes with a supracervical hysterectomy a small nubbin of endometrial tissue can remain behind and will bleed each month like a regular period used to. It is of no significance and shouldn't worry you and not worth having additional surgery or doing anything about it.