If you are living in Madina and you go to Jeddah at your relatives house from where you decide to perform Umrah. You wear the ihram and then perform your umrah, so is this right.
As for I know Dhu'l-Hulayfah is the miqat which is about 9 kilometers from Madinah and about 450 kilometers from Makkah. Dhu'l-Hulayfah is the miqat for those who live in Madinah and for those who approach Makkah from that direction.
Al-Johfa in the North-West for those going to Makkah from Jeddah. (Or, if it is difficult to go to Masjid-e-Johfa because of a valid reason, one can go to Rabigh, which is Mahaz-e-Miqat (in line of Miqat) and put on Ihraam there). It is about 115 Km from Jeddah on the way to Medina. Pilgrims arriving from Egypt, Syria and Southern Africa are required to enter into the state of Ihraam at this place.