It all started when my ni no Ito broke while tuning so I got a new one then it broke the second time I tuned it then broke again and again then now my san no Ito came loose.
Every time I tune my shamisen feels like a horror movie. Maybe I was too rough or rushed
Hi-ho.
If your strings frequently break you may have a rough spot on your koma, bachi, or kamigoma.
You may also be over-tightening or have old strings!
Please inspect your instrument and accessories for any sharp edges - and tell me where things are breaking.
I use to to over- tighten my strings resulting in breaks .
Which section of the string has the break been occuring? That may give some insight into the cause.
There was a dent on the kamigoma but luckily the issue has been resolved
Over-tighten? This has my attention because while I haven’t broken a string (what am I doing wrong? 
) I have wondered about the amount of tension required to reach tune. If the tuner is registering the correct tones (in my case mostly C-G-C) how do you know if it’s overly tightened? Is there a minimum string length?
well if it sounds correct and the tuner says its correct then dont keep tightening … LOL… I didnt have a tuner at some times and being a prepetual newbie I would keep twisting away …then snap …not sure about string length…