Flour sack towel inserts and Thirsties covers

Natasha

So my son is 6 weeks old and I have started using cloth with him. Using Thirsties covers and flour sack towel inserts along with a flannel insert and at night Bumkin minky inserts along with the FST inserts. I fold the inserts so there is more layers in the front and the legs seem to fit well. But it seems to still leak out when he pees especially out the top. But sometimes the sides! What am I doing wrong?

Please help!