still bfing, but want to give formula in sippy at meals

inluvwitcowboy

So here is my story.  I have been bfing with few issues, and no supply issues at all but my daughter will not nurse well during the day.  So I tried giving her a bottle of bm several times and she isn't interested in either.  Also when I am away she will only take a few ounces of bm in a bottle all day ( I work 10 hour days 3 days a week )  My mom tried to give bm in a sippy and she won't take it, even though she will suck down water or stonyfield baby yogurt drink with no problems.  My daughter is not even on the growth chart for weight so I am very worried about her not getting enough bm.  She eats solids fantastically. She has never had formula and I have considered giving her a sippy of formula and see if she would take that during the day while continuing nursing morning and night( rarely problems nursing at these times ).

What are your thoughts/experience with this?  Did your older baby have any digestive issues with formula?  Do you use the formula for older babies 9/10 months plus?