With DS1 I was advised to combination feed as he wasn't gaining weight as quick as he should be. I carried this on for months. Every feed on the boob followed by a bottle top up. The length of time on the breast decreased and he drank more from the bottle til I eventually gave up.
DS2 is 6 weeks old. Same problem. I've bought a double breast pump to try and increase my supply with the view to exclusively expressing if possible as I know he's probably used to the easier flow of a bottle by now, plus DP can join in with feeds.
I'm currently managing only 4-5 oz a day from several sessions. Any advice? I'm not even sure I'm pumping right!