Irregular periods. This a miscarriage?

Im 26 years old,married a year ago. Past I always had my periods regularly.in the month of jan I had my periods on 28th & next in the month of feb on 14th.with a gap of 14 days.later march & April it was as regular as before(28-30 days).Later I got my thyroid level (tsh:52.65 t4:8.00 t3:1.06)checked & Im on medication(Thyronorm 62.5mcg) since may 1st.In the month of may I din have my periods & started gaining a bit of weight.on june 2nd I got my periods & on 3rd I had severe pains like never before no tablet could stop the pain & to my surprise a large blood lump(flesh) kind of mass passed.then later the pain reduced but even after 4 days I feel the discomfort in my stomach & bad back ache. Was this a miscarriage?Due to hypothyroidism & as mentioned was gaining weight I was into rigorous exercise & physical activities in may specially after may 20th.