Still have feelings for my ex....

So I am in a very happy serious relationship at the moment with the most amazing guy I know. He lives with me we have bought baby animals together and I can’t picture my life without him.

But just recently my ex came back into my life. He’s not a bad ex and we are still really good friends but i feel like I just can’t get him off of my mind. And I really don’t know what to do!?

Is this normal? Has anyone experienced this? Can anyone suggest anything to help?

I don’t want to break up with my current partner at all. And I love him dearly, almost a little too much sometimes and the thought of doing so literally tears me up inside.

My ex is a very kind very understanding person and we have such a great friendship and I’m very close with his girlfriend as well.

I’m just so confused. I’m sorry if this makes no sense but I don’t know how to say it or what to do