Hey Renee,
I had similar trouble with both mine. Well, DS did lose weight and I did have to comp feed for a few months, but it all came good.
More recently with DD, she just stopped putting on weight at about 3 months and she stayed the same weight for a couple more months. We had a paed check for things and it all came back clear. We determined she was taking the 'right' amount of milk from me (by output and the weigh, feed, weigh again method) so paed was all happy with that and referred us to a dietician. In desperation, I have to say I did try topping her up with EBM and formula for a week but it made no difference whatsoever. After speaking to the dietician, she said that there are just some kids who are small but it was still important to get the calories in her as she'll need the extra energy for moving, crawling, etc.
We stuck with the breastfeeding, ditched the top ups after about a week and started solids at 5.5 months. I wanted to wait until 6 but I figured she obviously needs food so I thought that was better alternative than giving formula since she was only a couple weeks off starting anyway. We dived straight into solids - 3 meals a day, high calorie meals like meats, pastas, casseroles. You'd traditionally start with veggies and fruit but they aren't very high in calories. The dietician also got us to add more fat into her diet by adding olive or canola oil or a teaspoon of salt reduced margarine to her food for the extra calorie content. For us, this worked a treat and she gained 1kg in one month and is still slowly creeping back up to where she started on those graphs. At almost 9 months, she's about 6.8kg, still tiny but healthy and happy. Oh and she is no longer a chucky baby (she did chuck quite a bit in the early days, not huge ones, just frequent ones).
I'm not sure where you're at with your DS and if he's losing weight or just plateaued out. If he's losing weight, then he may need the top ups and there are ways to do this without compromising your supply. If he's just plateaued out has he started moving around a bit? Wriggling on the floor? Rolling over? DD just couldn't keep still when she was on the floor so used lots of energy. No one could explain for sure why she just stopped putting on weight.
Keep perservering, you're doing a great job. Don't be afraid of not doing something you aren't comfortable with. When I took DD to the hospital, all the senior paed said to me was "you don't have enough milk, put her on the bottle" that was that and sent me home with a referral to another paediatrician. I never followed her advice and I'm glad I didn't because DD & I are still breastfeeding perfectly fine. They didn't come and chase me down for not doing it. It was hard not to doubt my supply in those first few months but then I realised the more I try to fill her tiny tummy, it's just not going to fit and she's going to bring out the excess either top or bottom!
