From your multiple problems it seems that these are mainly due to,
1,This is puberty
age so there are hormonal
changes going on leading to profuse, irregular period, pain during period time and period early or late.
2, You have got hypothyroid.
So all problems are associated with your these two conditions.Diarrhea
you get might be due to ferrous sulphate
tablet, taking for anemia
There is also a possibility of having B12 deficiency.
So go for blood B12 estimation.
Wait for few months for your problems of period, if problem persisted then go for 3-4 cycles of hormonal medicine course after consulting your doctor.
Keep thyroid under control.
Ok and take care.