I am 42y did hysterectomy and removed ovaries now i have lower abd pain.like before i also had decapeptyle .is it possible that endometrioma is back?

Unlikely: I imagine that the surgery was for endometriosis and that you had similar pains before surgery. It is unlikely to have endometriosis recur after the ovaries are removed unless they are giving you estrogen replacement. Endometriosis can cause scarring and adhesions along with the surgery, and some of these pains may have to do with old scarring. An ultrasound may help, but may be other cause.