Wake windows and sleep

Hello there! I am a FTM of a 15 weeks old baby boy. I have a question in regards to wake windows and overtiredness. I have seen a few posts saying that wake windows are a myth and it has gotten me thinking and wondering if im doing the right thing. At every nap, my boy cries when I try to get him to sleep. He cries a little then stops,takes back the soothie and he seems sleepier, he does that 2 or three times until he falls asleep. It usually doesn't take long between 10 to 15 minutes and he would be out. Sometimes it does take longer. Is this normal?? He had a full week that he settled himself to sleep by himself with me only shushing and patting. This past week he hasn't done that at all. He would get close but then start crying so I rock him to sleep. He also used to sleep better, I would get 5 to 7 hours at night, now it's 3 and 4 if im lucky and with lots of wake ups and fussing during but not full on crying. Sometimes just giving him the pacifier does the job sometimes I pick him up and hold him and thats all he needs. Im having to Sometimes cosleep for him to stay asleep and not be so restless at night even tho his crib is attached to my bed. Another thing is that during the day he only contact naps on me, I've been trying to get him used to sleeping on his own, blacking out the room, sleep sack and white noise and I stay with him close by, but so far all my attempts have been a failure. Im wondering if he is going through a leap/regression or what. He already flips to his side on his own and has no trouble reaching for his toys on his play mat and grabbing toys and dragging them to his mouth. Other than that he is a healthy baby with no other issues and meeting all his milestones on time and sometimes even earlier. Im lost on what is right and what is not. Any help would be appreciated