6 month old not eating

[Torrennce]

I've had to return to work after 6 months on maternity. I hate it and to make matters worse my son won't eat when I am away. I will breast feed him before I go and he will refuse a bottle of my expressed milk and any purée that I have made, he won't eat until I return around half 5. I have tried giving the bottle when I am here aswell as trying to get him to eat purées but he won't have it, he won't have anything other than breast milk. I've had to come home from work early because of this and I know this can't happen long term. I work part time, 3 days per week and feel so guilty while I'm there as I know he isn't eating Any advice on how to get him to eat would be greatly appreciated