struggling to transition from EBF to bottle

Alexis
I have tried and tried to give my little one my pumped milk in a bottle and he refuses them all. We bought him all kinds of bottles and nope nada. I spend about 1-2 hours trying to bottle feed and he cries, chews on them or even wants to gag. He's three and a half months old. Any suggestions ? I go back to work in 4 weeks so I am so stressed out. 
Anyone had the same problem?