Welcome to HCM.
Left side of shoulder jt. pain should be ruled out as soon as possible at this age
Go for blood pressure,ecg check up to rule out any cardiac origin.
Otherwise you have seems to be muscular pain
.Go for complete blood count
,s.cal,s.b12.,RBS. Start oral calcium citrate
,d3 and multi vitamin tab.
Complete course of inj.B12 will be helpful.
Eat good nutritious,high calcium diet.
Consult your physician for better diagnosis and medical management.