Re:Need some life advice.
Mate i am in a similar situation with 2 little girls who are 3 and 1,my ex has not gotten herself another permanent partner as yet.
At first i couldn't deal with all the thoughts but everytime i go there my kids love seeing me,my 1 yr old puts her arms straight out to me,and looks so happy to see me.
My 3 yr old always says i missed you daddy etc.
So tbh i am just gonna do the best for them and not think about what is going on with there mum etc.
Keep building your bond with your child and have him as much as possible and forget these thoughts.
Or try and work things out with your ex,if it's too late just be strong and move on.
If you love something let it go,if it comes back to you it's yours,if it doesn't it never was.