In need of a advice or just someone to listen

To try to make a very long story short. My mom has been in a relationship with my stepdad for like 17 years, they got together when I was young so obviously that’s the Person I see as my dad, he left away for 6 year to do idk what and now he’s back and It’s being extremely hard to deal with to the point I feel like me and my moms relationship is ruined. He left when I was around 17or 18 I’m now 24 with two kids and adult and as I explained to my mom I feel like me and him lost that relationship but I they say I should feel like that so it’s kinda being ignored so it’s extremely awkward, it’s coughing arguments but I’m being the blame for it and it’s taking me to a really bad place and idk how to deal with it anymore, I’m at a point that I’m questioning if I’m crazy or have a problem being I’m being looked as if I have no reason to feel the way I do.