No Period...

So I'm just shy of 6 months postpartum and I was taking birth control pills for 3 months, but I haven't in about 2 months mainly because I keep forgetting to call. Anyways. I haven't had a period since the 13th of July of this year. I'm just a little concerned. I'm not pregnant because we use condoms and I already took some tests. My mom said that I should get my thyroid check because pregnancy and childbirth can mess with it? Should I go ahead and get checked? I've been told it can be the reason behind having an irregular period and a numbers of other things and I fit into a few of them.