HELP! Weak Nails

This is completely off the subject of periods etc...for the past couple of weeks I have been trying to grow my nails out but unfortunately they are very weak and snap/break easily🙄I used to have a habit of always chewing my nails when I was a kid and my Nan/Mom always used to use some varnish stuff to put on my nails to stop me from biting them so I have grown out of it now and the varnish never really worked for me. As I said earlier on in this statement in the past couple of weeks I have let them grow out but has the case of breaking...Can anyone please recommend anything to help my nails get stronger? Much appreciated, thank you🙂xx