Baby hasn't pooped in 4 days

My baby girl (nearly 6 weeks) hasn't had a BM in 4 days. She's very unhappy today and I think its because she hasn't gone. She's farting a lot and it reeks. She is mostly breastfed but has about 60ml of formula a day. She's refluxy so the doctor told us to try infant gaviscon. I gave her 3 doses in 48hrs but when she hadn't done a BM since I started I stopped it and she hasn't had any in 2 days. I asked my chn yesterday and she wasn't worried but with 4 kids I have never had one gone longer than 24hrs without one so I'm starting to be concerned, especially as she has been so unhappy today. I tried to give her some water but she wouldn't drink it. Don't know if I am freaking out over nothing

While it would be normal for a fully breastfed baby at this age, I'm not sure what is normal for a baby on formula as well. You could call the health info line, perhaps? Or maybe follow up with another health professional?

Gaviscon can be constipating for babies just like it can be for adults, so that will likely to be he cause. The amount of formula she has in relation to he total amount of milk she has in a day is very small, so I don't think th would be a huge factor. Try a warm bath, tummy time on your lap, tummy massage going in a clockwise direction, leg cycling or bending her legs up. If you are desperate you could try a glycerine suppository to move things along. If she starts vomiting more then usual, or it is a green colour, or her abdomen becomes hard and/or tender, then get her checked out.

We had the same thing and were told by midwife to put a spoon of brown sugar in 10 ml of formula that did the trick

Brown sugar works well, but it can be harsh, like giving her a strong laxative. If you need to give her gaviscon in the future, try to give her 10 - 20 ml water a day as well.

I think the gaviscon is what has done it. She was going every day until I started it. Will be seeing if the doctor can do anything else for her reflux. I have been massaging and trying to bicycle her legs but she gets quite upset when I do. She's finally asleep but when she wakes I might go have a warm bath with her. I'll see if I can syringe some water into her, she won't drink it from a bottle.