If you want the Melody superstar/perfect ending, you have to be with Melody ONLY, get all seven keys, and at least 385 points. If you want MFF/MFFF, then screw everyone that's friends with Melody (Sophia and Xianne)
You need 385 points if I remember correctly, to get the seventh key, AND you need to choose "Take the Lead" instead of "This is Your Chance" AAANNND you need to be ONLY, and I mean ONLY, on the Melody path for all that to happen (Koko, perfect ending, etc)
If you're short on points, then you made some wrong choices
If you want the good ending, where Melody has a kid, impregnate her on Week 14.
If you want to use a walkthrough to get a certain ending, check the attached file below