Problems switching 6mo DD over to formula - please help!

[Ditsy79]

Hi,
Just wanted some advice really.
I had been EBF-ing my DD who is now 25 weeks old. I am going back to work soon, and have been attempting to switch her over to formula - please don't flame me for that decision. I did consider expressing when I go back to work, but decided it wasn't for me.
Since Dd was about 6 weeks, we've been giving her a bottle of EBM every couple of days, so she would be okay taking a bottle. We were using medela Calma. 10 days ago I swapped her lunchtime BF for a bottle of formula (Aptamil 1 in an Agent natural bottle) - she was happily drinking between 5 and 6 ounces. So we thought we were going to be successful.
5 days ago we swapped another BF for formula, the early evening one. Again, it was all going okay...until yesterday.
Yesterday she was being a bit fussy with the bottle and would only take 4 ounces.
When I have tried her with formula this lunchtime, she has only taken 2.5 ounces, and is closing her mouth and pushing the bottle away.
I am obviously worried that she is not getting enough fluid and nutrients.
I wanted to swap feeds over to formula gradually so she would have time to adjust and to minimise the chance of mastitis etc for me, but now I'm not sure that I've done it the right way. Maybe I should have just gone cold-turkey and swapped all her feeds over at once?
We've been using the Aptamil powder at home, and the ready-made if we are out. DH has been doing the evening bottle, and I've been giving the lunchtime one as he is at work.
I just can't understand why she was fine with it for a week, and now seems to be rejecting the bottle. I'm finding it quite upsetting, and am on the verge of caving in and giving her my breast again (although this is not sustainable when I'm back at work).
Any advice would be very much appreciated!

*Avent not agent!

If you feed her before work and after work, I'm not sure how much she would need during the day. (It's been a long time). She would probably take more at these times as well. I would drop the early evening and just keep going with the lunchtime one.

Oh, also she may be teething or just off food today if she's not feeling 100%. Go back to 1 bottle and see if it's ok.

Thanks merry.
Forgot to say she had been having 6 bf's a day ( not sure if that is excessive for her age). So 5 or 6 am = bf, 9am = bf, 12 pm= ff, 3pm = bf, 6pm = ff, 9 pm = bf. My DH thinks she might be getting more BM now we've switched some feeds to formula, and therefore might be full when we're giving her the bottle - I don't know if that's true.

I think formula is more filling, so possibly she is full. It's great she isn't feeding in the night! Woweeeee. (She may pick up a night one when you back to work though).

There may be a couple of weeks where she's getting a bit less milk whilst she is adjusting, but I don't think you need to establish it perfectly before you go back to work as it will be harder for her to take the formula from you. I think 2 feeds from you and a good size lunchtime one for a while will be ok, and then she may go up to few more formula ones with whoever is caring for her.

Sorry, I don't think she is feeding too much. I meant drop the evening bottle for a bit rather than the evening feed.

We are currently switching to formula from bf with my 8mo dd and she has some mornings where she will only take 3oz and then 5oz the next day, I've started getting my husband to do some feeds and she will sometimes take more from him and I figure its because she can't smell the milk so will settle better.
I did use to worry but there's not a chance my little one is gonna go hungry, lol!!

I'm a little confused from your OP as to whether you're using the Medela or the Avent bottle for the formula so just as an aside in case it's useful: the Medela bottles are designed for EBM and can clog with formula, so it's worth checking if this is happening. Apologies if I've misunderstood.

Hi frumious. We were using Calma with ebm but have changed to Avent now that we are giving formula.
Thanks for your responses powla and merry. Think DD may not have been particularly hungry when I was trying to give her the bottle. It worked a bit better yesterday as I was using the premade stuff so was not so tied to times, IYSWIM.
Going to persevere with these two feeds, then swap another (hopefully by the weekend).