The baby gags when she starts eating! She takes the breast normally, g…

The baby gags when she starts eating! She takes the breast normally, grabs the areola, her lips turned out, you can see milk between them sometimes. But she makes a couple of gulps and then starts coughing and choking. Tried expressing before feeding with an electric breast pump, milk comes out, I express a little bit and feed him afterwards. All the same. Feeding in the usual position "cradle". Air gets swallowed and it's right in his tummy that he burps! Can't figure out what the problem is and how to deal with it? I have no more strength left! Every feeding lasts for a long time, I hold on several times... What am I doing wrong?!