Help! Need to get my milk going. Struggling with feeding

Hiya! My little boy is tongue tie but they can’t help him for another 2-3 weeks. He starts with a latch but can’t maintain as his tongue gets tired and he stops feeding. Then wants to cluster feed basically 24/7.

The midwife has suggested I give him

The breast until he gets tired so he stays familiar with latching but then finish him off with pumped milk.

Trying to pump while he only feeds 5 minutes doesn’t work because the milk isn’t ready in time. I have pumped more when I wait longer periods I’m between but now needing to do it every 2.5-3 hours.

Anyway- how can I get my milk supply up? And has anyone been in this situation where they can give tips and tricks.