There are two masturbation CGs (one solo, one with a dildo), three dream CGs, and one ending CG for the secret route

The dildo masturbation CG requires you to not masturbate until after you've talked to Dan and gotten him to help purchase a dildo (this is easier while you're on his route), since you can only unlock one masturbation CG per playthrough

The dream CGs require you to keep your libido high at certain points of the game... if you've found the Truth or Dare one, the other two are after the first frat party (get drunk during it) and a scene while you're not on Chris' route on March 10 if you attended James' play with Adam previously

There is a Dev Process Item that unlocks once you've completed the secret route that gives more explicit guidance for all of the CGs as well

I'm still missing 3 CGs.

I have no idea of when they are supposed to happen.

Would it be possible to know which week the CGs mentionned hereafter are supposed to take place ? 

1) "Watch Jake fulfill a fantasy" (Nate)

I suppose it's somewhere on the Jake & Nate Route

2) "Let your libido ruin a friendship" (Dan) [I guess that one must be very tricky :-D]

I suppose it must be on the Dan's Route

3) "Find new confort in an old friend" (Others)

I guess that's the one with Carlos & Adam