Relationship breakup

I have been with my partner for 4 years. Friends for 10 years. Very rocky relationship al throughout that time. We have a 2 year old and a baby expected on Christmas eve of this year. I have realised I am not in love with him and not sure how to go about it as we are expecting a baby in a short few weeks. I am not happy with him and it’s stressing me out. I do think it’s unfair if I keep it to myself and not tell him but I also think telling him is going to create a whole

Lot of unnecessary stress with baby coming and having to celebrate Christmas with his family. Has anyone been in a similar situation or have any advice?