Peter Bishop

I realize that a small change in a timeline could change major things over time, but when the observers did the time reset, in season 4 more specifically, there were no clues that they showed themselves nor that anyone knew about them. Yet, an observer is reponsible for all the changes in the main timeline and he's the reason that the alterntive peter died in the first place. If he did not show up, Walternet would not have been distracted and he would have seen that the medicine have worked, and Walter would not cross to the other universe to save him in the first place and the timeline would go like it was suppose to.. Am I missing something or is it a flaw in the series? This is killing me, please if any one knows, please answer this question.

So in the Original Timeline Walter loses Peter and after that he watches Alternate Peter and discovers that he is sick. He sits there and watches Walternate try and complete a cure when the observer distracts him from seeing that formula worked.

Now in the New Timeline Why does Walter cross over? I know it is to save him but If we look at the above and the observer does not interfere, there is no reason why Walternate would be distracted from seeing his cure work and saving Peter. My question is what prevents Walternate from curing his Peter?

I am so confused. If Peter really is in his original timeline, then why are certain things different that don't relate to him? For example, why is Rachel still married and have a girl AND a boy? And why can no one remember Peter? If anyone could help me with this conundrum, I'd deeply appreciate it. 

i thought that maybe thats why she looked at him plus that he shine. They have the same eye colour and we never saw Elizabeth pregnant.

Maybe Peter became an Observer, in other universe and timeline. It is possible right?