How to increase milk supply?

Hi Momshies! I'm a first time mom and working as well. For 7months exclusive breastfeeding ako and then last month nagmix na. Hindi na kaya ng milk supply ko ang demand ni baby. ??? But i still continue pumping sa office. But now napapansin ko na parang pakonti na ng pakonti milk supply ko. Your suggestions will be highly appreciated. Thank you in advance. ??