Found a lump?!?!

10 weeks ago I gave birth to a beautiful baby girl. But the other day my husband had found a lump in my breast.. I'm not breast feeding and have completely dried up... I've been to the doctors about it and they've given me tablets to help but should I be worried.. my breast absolutely hurts all the time and the lump is just getting bigger also this breast is 3 times bigger then my other breast.. what should I do?