how to top up with BM?

[Tumtitum]

My DD is ten weeks and currently hovering between 2nd and 9th percentile, having dropped from the 25th at birth. The health visitor is monitoring her weight fort nightly and top ups haven't been suggested yet but I know a few mums who have done top ups in the early days when their LOs weren't gaining weight.
I know from reading posts on here that I shouldn't be overly concerned as she is otherwise healthy, alert and does plenty of wet and dirty nappies. However, I think topping her up just a little would reassure me that she really is getting all she needs. I definitely don't want to use formula as I have plenty of breast milk to go around! However, I do find pumping a real chore and difficult with baby demanding a lot of attention!
Does anyone have any experiences of topping up to share? How much and how often?
Thanks

[Youremywifenow]

Mine is currently only 4 weeks but I had to top up as she had lost too much weight and would have been readmitted.
I used a syringe before a breast feed rather than after so she got a bit extra but would still go for a full breast feed. Generally 3-4 5 ml syringes worked. I used the calpol ones.