Dear Mam, I am 42 years old. In October 2016 I had my period on the 11th and in November 2016 I had my period on 4th. Today is 15 December 2016 and I haven't had my period ? Could I pregnant?

I suffer with thyroid. I take Eltroxin 1 milligram. Also my tummy is starting to feel like a bit heavy every now and again. I think it's after I eat ? I haven't taken a pregnancy test as yet. There was some light brown discharge every now and then.
Thank you so much for your kind assistance. Much appreciated.