This has happened with both mine around that age (currently enjoying it with DD2). It was just a phase with DD1 (and I assume this time too) and nothing to do with supply issues, she went on to feed till just after 3 through a pregnancy and with 6 months tandem feeding! It did last a few months and I think it is a symptom of the developing realisation of seperation between them and you, they just want to feel safe and close to mum!

We coslept which helped to feel more rested as I could doze a bit while they fed. My partner then gets up with DD2 in the morning so I can have an hour or two alone to sleep which also helps.

It is hard but it passes. Hope you can find a solution that works for you all.