mother cat back on heat and not bothering with kittens

my cats kittens are now 5 weeks old and the mother cat jess has come back into heat screaming to go out,she wont feed the kittens or bother with the kittens,should i put some milk down i bought from the vets for the kittens coz they aint feeding of momma cat, they have started to eat kitten food 3 times a day (wet) 

Yes, you can do so. they need good nourishment. Dont let the mama out, and I think you can even consider to spay her now as soon her heat is over.  After all, she is not caring much for the kittens any longer, and they had began to eat themselves.  When spaying done, she may even return to them, and at least wash them.

Good luck!