I suspect I may have Hypothyroidism…help!

My husband and I started TTC for the first time a few months ago. It’s been four cycles. I’ve been tracking my period and I started looking into this because I noticed that even though I have mostly regular length periods (31-32 days), my LP is very very short and when I looked up what causes a short luteal phase, it listed hypothyroidism as a possible cause. So I looked that up. There are lots of symptoms I’ve had that may be hypothyroid (possibly clinical but possibly sub-clinical), but there are so many symptoms that could be caused by other things—it’s tough to tell! But I also just found out it runs in my family. My aunt and grandmother (both of whom I take after physically) both have it, apparently. So now I’m taking it more seriously.

I haven’t had my TSH levels checked yet but I have an appt with my GP on the 11th. What do I need to tell her or ask for in order to get tested? Should I make an appointment with a fertility specialist or endocrinologist? What should my course of action be?