lol you are running a 20 week cycle yes? if its test e or c then you wait 2 weeks from your last injection to start pct, pct should be run for lets say 5 weeks, when that is finished (you have already been off 7 weeks, (2 after last injection and 5 for pct = 7 weeks)
THEN you wait the 20 weeks untill you should cycle again so your 7+20 = 27 weeks off