I am having trouble with the construcción of these types of sentences. Is it "Estoy esperando a que mi novio abre la puerta"? Or do you use the unconjugated abrir?
That's almost right. You need the subjunctive mood for abrir (i.e. abra) because you're describing an irrealis situation. The correct sentence would be:
Estoy esperando (a) que mi novio abra la puerta.
It is common to drop the preposition a in some countries such as Argentina or Chile, as per the comments, while it is kept in Spain.