my baby sometime doesn't want to breastfeed

She never tried bottle milk she only tried pumped milk once.. for the first month we used nippleshield but when we stop using it i wasn't a problem.. she is 2 1/2 month.. every day she don't wanna be fed for about 3-4 hours and she olny do the other breast and not the other one.. when she doesn't want to be fed we have to but her to sleep first then try to feed her.. sometime it take many hours to try to do that... what can i try to do? i hope you can understand my writing.. English is not my first language