Breastmilk in bottles?

My baby is almost 7 weeks old and has been having bottles sporadically for a couple weeks (pumped breastmilk) and ever since then, he's been fussier with the breast and only nurses for like 5 mins at a time :( he does a lot better with a bottle. I'm going back to work in a few weeks and plan to pump at work...if he's doing better with bottles should I just stick with that and exclusively pump? Since he'll be taking bottles while I'm at work anyway?