Belly button is called naaf in urdu. I don't know what your friend is taking about though. Leg cramps can be indicative of some serious issue. I would go to a specialist and get it checked. If it is only due to weakness then doc would tell you about dietry suppliments.
But they also say..that your uturus can be weak and then your legs hurt ..i know some aunties that give some speacial jari butiya to theyr daugthers to help them...and have a strong uturus ??? sounds strange isnt it ..
before taking anything herbal, i would seriously consult a homeopathic doctor or a naturopath first… i.e. someone qualified who’s studied that sort of thing, and not some aunty up the street who got the remedy from who knows where. this is your health, after all, you don’t want to mess with it.
this is one of the things that comes up on google when you search for uterus and leg pain- Uterine Fibroids-Symptoms
what is says is that an inflamed uterus (i guess it could be classified as weak) can lead to pain of all sorts (including in your legs) and period irregularity. maybe you should go get a second opinion and insist on an ultrasound to see exactly what is going on.